go flat—
1. spread out lying at full length:
- I would usually go flat on the ground in case the door was trapped with a grenade.
2. (coll.) lose enthusiasm or interest:
- I get quite interested for about five minutes and then—poof! I go flat like a burst balloon.
3. (of a battery) run down; lose charge:
- Darren has called the Automobile Association twice: once when the battery went flat….
4. (of a tire) be deflated (after a puncture):
- After driving on the freeway, all four of Torty’s tires went flat.
5. (of beer) lose flavor; become stale:
- Not only will the beer suddenly go flat: the extra oxygen will rapidly burn the alcohol out of the client’s bloodstreams.
go flat out—(coll.) do smth. with all one’s energy:
- Our vote is holding up well and we will be going flat out to win over the undecided voters.