Below are definitions of expressions that sometimes appear in profiles

Straight - slang for "heterosexual".

Bisexual - sometimes abbreviated to "bi".
Note that "bi-curious" means straight/heterosexual with fantasies of same sex relations.

Gay - slang for "homosexual".

Heteroflexible - homosexual behaviour, despite being primarily heterosexual.

Homoflexible - heterosexual behaviour, despite being primarily homosexual.

Pansexual - not limited in sexual choice with regard to biological sex, gender, or gender identity.

Asexual - a person who has no sexual feelings or desires.

BDSM - an abbreviation for "bondage, discipline, sadism, masochism".

B&D - an abbreviation for "bondage & discipline".

S&M - an abbreviation for "sadism & masochism".

CP - an abbreviation for "corporal punishment".

Lesbian - gay female.

Transgender (or TG) - men or women who identify or enjoy dressing as the opposite sex.

Transsexual (or TS) - a person whose sexual identification is entirely with the opposite sex.
MTF TS = Male to female transsexual, FTM TS = female to male transsexual.

Transvestite (or TV) - wears clothing of the opposite sex.

Cross dresser (or CD, or XD) - wears clothing of the opposite sex.

Fetish - obsession or unusual sexual interests.

Swinger - usually associated with couples or groups. Partner swapping. Wife swapping.

Polygamy - more than one wife or partner, polyamory.

Cuckold - a man whose wife committed adultery.

GSOH - Good sense of humour.

LOL - Laughs out loud.

LMAO - Laughing My Arse Off.

ROTFL - Rolling On The Floor Laughing.