in the least is an adverb meaning "to any extent at all". It carries 2 recorded senses.
in the slightest degree or in any respect
“Are you at all interested? No, not at all”
“was not in the least unfriendly”
Definitions, synonyms and semantic relations for in the least come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.