1 to become or make sth become flat or flatter:
[V] The cookies will flatten slightly while cooking. * [VN] These exercises will help to flatten your stomach. * He flattened his hair down with gel. * The bird is recognizable by its flattened beak. * Roll the dough into balls and flatten slightly.
2 [VN] to destroy or knock down a building, tree, etc:
Most of the factory was flattened by the explosion.
3 [VN] (informal) to defeat sb easily in a competition, argument, etc:
Our team was flattened this evening!
4 [VN] (informal) to hit sb very hard so that they fall down:
He flattened the intruder with a single punch. * I'll flatten you if you do that again!
5 [VN] (music) to sing or play a note lower
PHRASALVERBS
flatten sth / yourself against / on sb/sth to press sth/your body against sb/sth:
She flattened her nose against the window and looked in. * Greg flattened himself against the wall to let me pass.
flatten out
1 to gradually become completely flat:
The hills first rose steeply then flattened out towards the sea.
2 to stop growing or going up:
Export growth has started to flatten out.
flatten sth<->out to make sth completely flat
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