Word forms: plural thongs1. countable nounA thong is a long thin strip of leather, plastic, or rubber.
2. countable nounA thong is a type of underwear, or the bottom of a bikini, that is very narrow at the back.
3. countable noun [usually plural]Thongs are open shoes which are held on your foot by a V-shaped strap that goes between your big toe and the toe next to it.
[mainly US]regional note: in BRIT, usually use flip-flops