A joke -- monorail? (3-5)
I believe the answer is:
one-liner
This could be a double definition.
'a joke' is the first definition.
(I've seen this before)
'monorail?' is the second definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
Can you help me to learn more?
(Other definitions for one-liner that I've seen before include "Witty remark contained in a single sentence" , "Flat, smooth" , "Single sentence jokes" , "Quick gag" , "Short joke - witty remark" .)