A spectator or supporter who habitually jeers or finds fault; especially (in plural) a section of a particular team's support which behaves in this manner.
Origin
1960s; earliest use found in The Times.
Definition of boo-boy in US English:
boo-boy
noun
British Sport Association Football
A spectator or supporter who habitually jeers or finds fault; especially (in plural) a section of a particular team's support which behaves in this manner.