The term 'underlying meaning' can be defined as the hidden or implied message behind a text. In this context, two crossword solutions for this term are 'DRIFT' (5 letters) and 'subtext' (7 letters). DRIFT is a verb that means to move slowly in a particular direction, often without any conscious control. Subtext, on the other hand, is a noun that refers to the underlying meaning of a text, which may be different from the literal meaning of the words.