look up any word, like bae:
 
1.
slow, not smart. Not stupid, just not quick on the uptake.
I closed in for a kiss, but ed was a bit flat-headed and failed to pick up my cue.
by henrysfeelingfine January 03, 2007
4 1
 
2.
otherwise known as; to be a Flathead. basically meaning slutty, jerky, or diddlerish.
Girl #1: so..me and adam hooked up today..
Girl #2: are you guys dating?
Girl #1: no.
Girl #2: *gasp* that's so Flatheaded of you!
by diddlegirl69 February 17, 2010
1 0