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An exceptionally conceited or arrogant person. He turned into a real swellhead after his books became so popular. I'm really tired of these self-important swellheads coming in here and telling us how to do our jobs.
Exceptionally conceited or arrogant. He's been getting really swellheaded ever since his books started selling well. I'm really tired of these self-swellheaded executives coming in here and telling us how to do our jobs.
See also: swellhead
n. a conceited person. Tom is getting to be such a swellhead.