Definition of on spec
1 : without having a definite buyer or customer but with the hope or expectation of finding one when work is completed He built the house on spec. She wrote the script on spec.
2 chiefly British : without being sure of success but with the hope of success He wrote to the company on spec, hoping for a job.
Seen and Heard
What made you want to look up on spec? Please tell us where you read or heard it (including the quote, if possible).