Heads will roll

If heads will roll, people will be punished or sacked for something that has gone wrong.

Headstrong

A headstrong person is obstinate and does not take other people's advice readily.

Healthy as a horse

If you're as healthy as a horse, you're very healthy.

Heap coals on someone's head

To do something nice or kind to someone who has been nasty to you. If someone felt bad because they forgot to get you a Christmas gift, for you to buy them a specially nice gift is heaping coals on their head. ('Heap coals of fire' is also used.)

Hear a pin drop

If there is complete silence in a room, you can hear a pin drop.

Hear on the grapevine

To receive information indirectly through a series of third parties, similar to a rumour.

Hear something on the grapevine

If you hear something on the grapevine, you are informed about something by someone, circulating information or gossip from one person to another informally. ('Hear it through the grapevine' is also used.)

Hear something on the jungle telegraph

(UK) If you hear something on the jungle telegraph, you pick up some information or informal gossip from someone who shares some common interest.  ('Bush telegraph' is also used.)

Heart in the right place

If someone's heart is in the right place, they are good and kind, though they might not always appear to be so.

Heart in your boots

If you're heart is in your boots, you are very unhappy.

Heart in your mouth

If your heart is in your mouth, then you feel nervous or scared.

Heart isn't in it

If your heart is not in something, then you don't really believe in it or support it.

Heart misses a beat

If your heart misses a beat, you are suddenly shocked or surprised. ('Heart skips a beat' is an alternative)

Heart of glass

When someone has a heart of glass, they are easily affected emotionally.

Heart of gold

Someone with a heart of gold is a genuinely kind and caring person.

Heart of steel

When someone has a heart of steel, they do not show emotion or are not affected emotionally.

Heart-to-heart

A heart-to-heart is a frank and honest conversation with someone, where you talk honestly and plainly about issues, no matter how painful.

Heath Robinson

(UK) If a machine or system is described as Heath Robinson, it is very complicated, but not practical or effective, named after a cartoonist who drew very complicated machines that performed simple tasks.

Heaven knows

If you ask someone a question and they say this, they have no idea.

Heaven knows

Used when someone does not feel recognized or appreciated. For example; heaven knows how hard I work to feed my family.

Heaven only knows

The answer to a question is not or cannot be known. For example, heaven only knows when the war will end.

Heavenly bodies

The heavenly bodies are the stars.

Heavy-handed

If someone is heavy-handed, they are insensitive and use excessive force or authority when dealing with a problem.

Hedge your bets

If you hedge your bets, you don't risk everything on one opportunity, but try more than one thing.

Hell for leather

If you do something hell for leather, especially running, you do it as fast as you can.

Hell in a handcart

If something is going to hell in a handcart, it is getting worse and worse, with no hope of stopping the decline.

Herding cats

If you have to try to co-ordinate a very difficult situation, where people want to do very different things, you are herding cats.

Here today, gone tomorrow

Money, happiness and other desirable things are often here today, gone tomorrow, which means that they don't last for very long.

Hide nor hair

When there's no trace of something or a person, you haven't seen hide nor hair of it or them.('Neither hide nor hair' is also used.)

Hiding to nothing

If people are on a hiding to nothing, their schemes and plans have no chance of succeeding. 'Hiding to nowhere' is an alternative.

High and dry

If you are left high and dry, you are left alone and given no help at all when you need it.

High and low

If you search high and low, you look everywhere for something or someone.

High and mighty

The high and mighty are the people with authority and power. If a person is high and mighty, they behave in a superior and condescending way.

High as a kite

If someone's as high as a kite, it means they have had too much to drink or are under the influence of drugs.

High on the hog

To live in great comfort with lots of money.

High-handed

If someone is high-handed, they behave arrogantly and pompously.

High-wire act

A high-wire act is a dangerous or risky strategy, plan, task, etc.

Highway robbery

Something that is ridiculously expensive, especially when you have no choice but to pay, is a highway robbery.

Himalayan blunder

A Himalayan blunder is a very serious mistake or error.

Hindsight is twenty-twenty

After something has gone wrong, it is easy to look back and make criticisms.

Hit a nerve

If something hits a nerve, it upsets someone or causes them pain, often when it is something they are trying to hide.

Hit and miss

Something that is hit and miss is unpredictable and may produce results or may fail.

Hit home

If something hits home, it is understood completely and has a strong effect as people accept it even though it is negative.

Hit me with your best shot

If someone tells you to hit them with your best shot, they are telling you that no matter what you do it won't hurt them or make a difference to them.

Hit rock bottom

When someone hits rock bottom, they reach a point in life where things could not get any worse.

Hit rough weather

If you hit rough weather, you experience difficulties or problems.

Hit the airwaves

If someone hits the airwaves, they go on radio and TV to promote something or to tell their side of a story.

Hit the books

If you hit the books, you study or read hard.

Hit the bull's-eye

If someone hits the bull's-eye, they are exactly right about something or achieve the best result possible. "Bulls-eye" and "bullseye" are alternative spellings.

Hit the ceiling

If someone hits the ceiling, they lose their temper and become very angry.

Hit the Dirt

To duck out of the way or fall to the ground to avoid something dangerous.

Hit the fan

When it hits the fan, or, more rudely, the shit hits the fan, serious trouble starts.

Hit the ground running

If someone hits the ground running, they start a new job or position in a very dynamic manner.

Hit the hay

When you hit the hay, you go to bed.

Hit the mark

If someone hits the mark, they are right about something.

Hit the nail on the head

If someone hits the nail on the head, they are exactly right about something.

Hit the right note

If you hit the right note, you speak or act in a way that has a positive effect on people.('Strike the right note' is also used.)