1
general::
1. At once, without delay, as in When the boss learned Tom had been lying, he fired him on the spot. This usage suggests that one does not have time to move away from a particular spot. [Late 1600s] 2. At the scene of action, as in Whenever there's a bad accident or fire, you can be sure the station will have a reporter on the spot. This usage Also employs spot in the sense of "a particular location." [Late 1600s] 3. Under pressure or in trouble, as in He's on the spot, because he can't pay back the loan. It is Also phrased as put on the spot, meaning "put under pressure." For example, The reporter's question put her on the spot; she didn't want to lie or to admit her part in the scandal. [First half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): on the spot
1. Lit. at exactly the right place; at exactly the right time. • It’s noon, and I’m glad you’re all here on the spot. Now we can begin. • I expect you to be on the spot when and where trouble arises. 2. Fig. in trouble; in a difficult situation. • There is a problem in the department I manage, and I’m really on the spot. • I hate to be on the spot when it’s not my fault.
McGrawhill's American Idioms And Phrasal Verbs