on spec

Từ điển Oxford Advanced Learner 8th

on ˈspec idiom
(BrE, informal)when you do sth on spec, you are trying to achieve sth without organizing it in advance, but hoping you will be lucky
•A lot of young people apply for jobs on spec (= not in reply to an advertisement, but hoping that a job might be available).
Main entry: ↑spec_idiom