1make or become flat or flatter: [with object]:her hair had been flattened by the storm [no object]:after Kendal, the countryside begins to flatten out
[with object and adverbial of place] press (oneself or one’s body) against a surface:Guy flattened himself against the wall
2 [with object] raze (a building or settlement) to the ground:the entire town centre was flattened by the 500 lb bomb
informal strike (someone) so as to make them fall down:Flynn flattened him with a single punch
informal defeat heavily in a contest:they flattened Bridgend by forty-two points to fifteen
informal humiliate or depress (someone):the controversy has flattened everybody here
3 [with object] Music lower (a note) in pitch by a semitone.
flatten out
1(of an increasing quantity or rate) show a less marked rise; slow down:over the last two years our sales increase has flattened out
2make an aircraft fly horizontally after a dive or climb:he flattened out and made a fine three-point landing
