noun
subleader; assistant leader
A person who supports or acts as a deputy to the main leader, often in teams, clubs, or organizations.
彼はチームのサブリーダーとして、リーダーをよく支えている。
As the team's subleader, he supports the leader well.
Variant with a middle dot; less common but still seen.
リーダー is the main leader, while サブリーダー is the deputy or assistant leader.
Loanword from English 'subleader'.