an/(one's) old flame
One's former lover. How am I supposed to forget about my old flame if I keep seeing her around town? Yeah, Ben is his old flame—they dated last summer.
an old flame
COMMON An old flame is someone who you had a romantic relationship with in the past. Last week Alec was seen dining with his old flame Janine Turner in New York. Note: An old meaning of `flame' was the person that someone was in love with.
an old flame
a former lover. informalan old ˈflame
(informal) a person you were once in love with; a former boyfriend or girlfriend: My mother has an old flame who sends her a bottle of perfume once a year.old flame
n. a former sweetheart or lover. It is best to forget an old flame.