What does it mean to “shoehorn something in”?

A shoehorn is a device used to help someone put a shoe (particularly a tight shoe) on to their foot.

So ‘to shoehorn something in’ is an idiom about putting something (or someone) into a tight situation.

Example: ‘Her schedule was very busy, but she managed to shoehorn him in’ means that although she was very busy she managed to find time for an appointment with him. This is probably the most common usage, but it can also be used in other situations:

Example: ‘I shoehorned myself into their conversation’ means that two or more people were talking but I was able to join in.

Example: ‘They didn’t want to talk about work but I shoehorned it into the conversation’, means they were talking about something else but I managed to raise the subject of work.