Noun | 1. 5 - the cardinal number that is the sum of four and onecinque, fin, five, fivesome, Little Phoebe, pentad, Phoebe, quint, quintuplet, quintet, Vdigit, figure - one of the elements that collectively form a system of numeration; "0 and 1 are digits" | Adj. | 1. 5 - being one more than four five, vcardinal - being or denoting a numerical quantity but not order; "cardinal numbers" |