From WordNet (r) 3.0 (2006):
boo
n 1: a cry or noise made to express displeasure or contempt
[syn: boo, hoot, Bronx cheer, hiss, raspberry,
razzing, razz, snort, bird]
v 1: show displeasure, as after a performance or speech [syn:
boo, hiss] [ant: acclaim, applaud, clap, spat]
