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1. Rude or arrogant. If you say something bigheaded like that in the meeting, you won't make many friends here.
2. Feeling the effects of a hangover. If you drink too much tonight, you'll definitely be bigheaded tomorrow.
1. mod. conceited. What a bigheaded jerk!
2. mod. having a hangover. I feel sort of bigheaded. Too much beer, I guess.