Geeks and nerds often have it rough in the romance department, especially in popular culture. Typically, they are stereotyped as being so unattractive that only fellow nerds would find them desirable mates. However, it is interest and intellect that make the nerd, not looks. For some folks, intelligence is very, very attractive.
Other names for this trope would be sapiosexual, scisexual, and cognisexual.
This trope shows what happens when a character finds that a nerd is, indeed, sexy. The nerd's "objective" looks could fall anywhere within the wide spectrum of human attractiveness. All that matters is that a character finds something about the nerd that arouses their interest.
Compare Endearingly Dorky, where characters are charmed by dorks (who may or may not be nerds as well). See also Hot Librarian, Brains and Bondage, Geeky Turn-On, Bespectacled Cutie, Glasses Are Sexy, Nerdcore, Lovable Nerd and Give Geeks a Chance. Racial/nerd tropes like Jewish and Nerdy and Asian and Nerdy are examples of ethnicities associated with intelligence.
Only add examples that are acknowledged in-universe.