The term 'least adequate' can be described by two crossword solutions: 'barest' (6 letters) and 'scantest' (8 letters). Both words refer to having the least amount of something, or being the most inadequate. Barest is an adjective meaning having the least amount of something necessary or desirable, while scantest is an adverb meaning to the smallest degree or extent. Together, these two words describe the concept of having the least amount of something, or being the least adequate.