Does "dinner thing" have a meaning of "dinner plans" or "dinner date"?
Yes, "dinner thing" refers to any gathering, event, or plans which involved dinner. It is a very vague way of saying "dinner" because the word "thing" makes it uncertain who or what kind of dinner event it was. Thus, "dinner thing" is often used as an excuse or when trying to get out of plans. Ex: I'm late to your party because I had a dinner thing. Ex: Sorry I can't go out on a date with you because I have a dinner thing. Ex: I have to go because I have a dinner thing.