A person considered to have been born on a cusp between significant generations(noun)
A person born on a day at a junction of star signs(noun)
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Use "cusper" in a sentence
"Baruchel's one of those yet to break out -- he calls himself a perpetual "cusper," since promises of a breakthrough (most recently in fellow Apatow alum Ben Stiller's "Tropical Thunder") never actually happened, which doesn't bother him."