Bi-curious is a term for a person, usually someone who is a heterosexual, who is curious or open about engaging in sexual activity with a person whose sex differs from that of their usual sexual partners. The term is sometimes used to describe a broad continuum of sexual orientation between heterosexuality and bisexuality. Such continuums include mostly-heterosexual or mostly-homosexual, but these can be self-identified without identifying as bisexual. The terms heteroflexible and homoflexible are mainly applied to bi-curious people, though some authors distinguish heteroflexibility and homoflexibility as lacking the "wish to experiment with sexuality" implied by the bi-curious label.
The term started becoming popular after 1984, according to Merriam-Webster, but The New Partridge Dictionary of Slang and Unconventional English and Oxford Dictionaries' Lexico claim that the term was coined in 1990.
Characterized by an openness to or curiosity about having sexual relations with a person whose sex differs from that of one's usual sexual partners : curious about exploring or experimenting with bisexuality.
The term 'bi-curious' refers to that fact that many people who are basically straight might consider an occasional homosexual adventure simply to broaden their horizons.
Someone who considers themselves heterosexual but has a sexual or romantic 'curiosity' toward the same gender.