quartet

noun

1. 1

   a musical composition for four performers

2. 2

   four people considered as a unit

   he joined a barbershop quartet

   the foursome teed off before 9 a.m.

3. 3

   a set of four similar things considered as a unit

4. 4

   four performers or singers who perform together

5. 5

   the cardinal number that is the sum of three and one