Cupid's bow feature on a human lip
The Cupid's bow or tubercle is a facial feature where the double curve of a human upper lip is said to resemble the bow of Cupid, the Roman god of erotic love. The peaks of the bow coincide with the philtral columns giving a prominent bow appearance to the lip.
The phrase is common in literature, often used related to speech, and therefore the mouth, as in Shakespeare's Venus and Adonis:
- For pity now she can no more detain him; (577)
- The poor fool prays her that he may depart:
- She is resolv'd no longer to restrain him,
- Bids him farewell, and look well to her heart, (580)
- The which, by Cupid's bow she doth protest.
Medical significance 
Newborn babies with Fetal Hydantoin Syndrome, a consequence of using Hydantoin and/or its major derivatives Phenytoin, Dantrolene and Fosphenytoin, can present with the Cupid's bow defect known as cleft lip.
A study by the University of the West of Scotland conducted through an online survey found that women with pointy or prominent cupid's bows were more likely to experience orgasm during sex.
See also