spec

spec /ˈspɛk/ noun
plural specs
spec
/ˈspɛk/
noun
plural specs
Britannica Dictionary definition of SPEC
: a detailed description of work to be done or materials to be used in a project : specification
[count]
— usually plural
[noncount]
(US)

on spec

1 
: without having a definite buyer or customer but with the hope or expectation of finding one when work is completed
2 
chiefly British : without being sure of success but with the hope of success