As long as your synonyms each map back to exactly one "actual" or core word, what you have is fine. Then it's just
select ACTUAL from Your_Table where SYNONYM = "The_Search_Term"
and you'll get back zero or one records.
I might use a like
clause instead if your synonyms are dissimilar enough, so you don't need to mess with plurals:
select ACTUAL from Your_Table where SYNONYM like "%The_Search_Term%"
That way you don't need to include both flame
and flames
; flame
will work for both.