Relative term
A relative term was a word or phrase that had multiple meanings or was dependent on comparison to another thing.
In 2267, after Doctor Leonard McCoy bemoaned his failure at getting Eleen to want her baby, Spock said that "Virtue is a relative term." (TOS: "Friday's Child")
(TNG: "Time's Arrow")
(VOY: "Sacred Ground")
(VOY: "Blood Fever")