The term "sub" has multiple meanings depending on its context.
1) In a BDSM (Bondage, Discipline, Sadism and Masochism) relationship, it refers to someone who is being dominated or controlled by another person in the relationship. This can involve various power exchange dynamics such as submission, where one partner gives up control to their dominant partner for mutual pleasure and satisfaction.
2) In a more general sense, "sub" may refer to something that is secondary or subordinate, such as being a member of a group or team that supports the main focus or goal. For example, in music, "sub" can be used to describe an instrument or sound that plays a supporting role to the melody or lead part.
3) In some online contexts, particularly within gaming communities, "sub" may refer to being a supporter of another player or team, often through donations or other forms of support.