singlet

noun7

1. •
   (UK, Australia) A sleeveless buttonless shirt with a low-cut neck.

   • However, even in the latter he wears a blue singlet to help remind the audience of his working-class roots. — 2006
2. •
   A single piece of clothing
3. •
   A set of one, an item not part of a larger set
4. •
   A multiplet having a single member, especially a single spectroscopic peak.
5. •
   A quantum state having zero spin.

   • When a ground state molecule absorbs a photon, the values of the electron spins are not altered and thus the primary excited state is the singlet state. — 2003
6. •
   A person who does not have a form of multiplicity; a single self or personality occupying one human body.

   • Her system started when she was 17 years old: “We were not created by trauma. It started from being a singlet (one body, one person), but then, we lost our sense of self. […] — 2017
7. •
   A one-piece, tight-fitting uniform, usually made of spandex or nylon, required in wrestling and powerlifting.