From Longman Dictionary of Contemporary Englishgirlfriendgirl‧friend /ˈɡɜːlfrend $ ˈɡɜːrl-/ ●●● S3 noun [countable] 1 GIRLFRIEND/BOYFRIENDa girl or woman that you are having a romantic relationship with → boyfriend He’s never had a girlfriend.somebody’s girlfriend He lives in Chicago with his girlfriend.split up/break up with your girlfriend (=stop having a romantic relationship) one of my ex-girlfriends (=former girlfriends) I didn’t have a steady girlfriend (=one you have a long relationship with).2 especially American EnglishFRIEND a woman or girl’s female friend She’s out with one of her girlfriends.THESAURUSgirlfriend a girl or woman that you have a romantic relationship with, especially for a fairly long timeKatherine was his first girlfriend.partner the person you are married to, or the person you are living with and having a sexual relationship withHe brought his partner along to the party.old flame informal someone who was your girlfriend or boyfriend in the pastI found a love letter from one of his old flames.mistress a woman that a man has a sexual relationship with even though he is married to someone else. Often used when the man is famous or powerfulThe president had a mistress for many years.lover someone who you have a sexual relationship with, but who you are not married toHe was going to meet his secret lover.fiancée the woman who a man is going to marryRod plans to marry his fiancée later this year.ex informal a man’s former wife or girlfriendMy ex looks after the children on Thursdays.be going out with somebody if you are going out with a girl or woman, she is your girlfriendShe’s going out with a guy she met at work.
Examples from the Corpus
girlfriend• an ex-girlfriend• I wish I had a girlfriend who'd hug and kiss me when I was going to catch a train.• Does Mark have a girlfriend?• Katherine is his first girlfriend since breaking up with Maggie.• The cottage on the left here was bought by some business type who was going to weekend here with his girlfriend.• I rushed off to tell my girlfriend at her Catholic convent in Berkshire.• Seth is bringing his new girlfriend to Heidi's party.• I met my brother's new girlfriend last night.• Wendell hasn't had a steady girlfriend in years.• Stumped for ideas and bewildered over all those girlfriends who lacked belief in him, Henderson decides to psychoanalyze his problems.had ... girlfriend• He had a girlfriend but has dumped her for me and is being really sweet.• I wish I had a girlfriend who'd hug and kiss me when I was going to catch a train.• I had a girlfriend at school - Sara, her name was.• I had a girlfriend, Lisa DeLarios, who went to New York, and was doing great stand-up comedy.• It's a street his sister admits he knew, had a girlfriend there.• Relaxed laws make Vegas the home of quickie weddings, although Jackson himself has never had a girlfriend. 