1. The biological sex with which a person identifies, or is identified: see also gender identity.
2. (sexual orientation) An individual's sexual preference or orientation as heterosexual, homosexual, or bisexual as part of their sense of identity. Foucault and others have argued that homosexuality as a basis for identity (‘being homosexual’), as opposed to engaging in sexual activities with those of the same sex, is historically a very recent one: the term ‘homosexual’ was first devised only in 1869.