Say I want to find an idiom that means wasting time/effort, now if I were to search Google or a dictionary with the query
An idiom that means wasting time/effort
I would get idioms that actually contain the words "wasting", "time" or "effort" in them, but may or may not (often not) mean wasting time/effort.
Thesaurus or search engine, they wouldn't return the idiom "flog a dead horse" which could be the correct answer to my query "An idiom that means wasting time/effort".
So, is there a way to search by meaning?