- Brit. a man's undershirt, esp. a sleeveless one
- Austral., N.Z. a short-sleeved or sleeveless knit top, as a T-shirt or tank top
- an atom that is freed from combination by being raised to a higher energy level
Origin of singlet; from single, modeled on doublet
- Chiefly British A man's jersey undershirt.
- Physics A multiplet with a single member.