What does "年下" mean?

在耽美（BL中），年下，指攻的年纪比受小。衍生有年下攻、年下文等词

ENIn BL, 'niánxià' refers to a relationship where the dominant partner is younger than the receptive partner. Derived terms include 'niánxià gōng' (younger top) and 'niánxià wén' (younger top story).