From The Collaborative International Dictionary of English v.0.48 :
no-go \no-go\ adj.
not functioning properly or in suitable condition for
proceeding; as, the space launch was no-go. Opposite of go,
a.
[WordNet 1.5]
From WordNet (r) 3.0 (2006) :
no-go
adj 1: not functioning properly or in suitable condition for
proceeding; "the space launch was no-go" [ant: go]