It's water under the bridge.

it's Contraction

— The contraction of "it is". Bring you coat. It's raining. "Where's the book?" "It's on the teacher's desk." "What's that?" "This? It's just a piece of paper." — The contraction of "it has". It's been a long time since I've had cake.

water Noun

— Water is a clear liquid of the chemical compound Hsub2/subO that all living things need in order to live. The dog drank the water from his dish Can I please have a glass of water? Your plant needs more water as it is about to die. — A water is a bottle or glass serving of water. "I want to order two waters, waiter". — Water is mineral water. — Water is one of the four basic elements. — Water is urine. — Water is amniotic fluid. Right before the woman went into labor, her water broke.

water Verb

— If you water something, you add water to soil around plants. He waters the plants. — If you water something, you give water to animals. He waters the horses. — If you water something, you dilute it. — If something waters, it fills with water; it secretes water. His eyes watered as he cut up the onion.

under Preposition

— In the same place as another thing, but lower. They ate under the trees. — In the control of. He was under the leader of the organization. — In the middle of a process; experiencing. The idea is under the committee's judgement (judging).

the Determiner

— Used, instead of a, to reference something specific, already known to exist. Compare "I read a book." and "I read the book." — Used with a stress, to show that the word following is special. Are you the John Smith that I went to school with? — Used with an adjective that acts like a noun to mean all of the people concerned The poor are always with us. — Used with superlatives forms of adjectives and adverbs. You are the best.

bridge Noun

— Anything which avoids something which blocks a path, usually water, by going over the top of it. The connects the two sides of California. The bridge let cars go over the road, to avoid the traffic. — A card game.