Definitions
1.AdjectiveEssential or central; of great importance or relevance."He was instrumental in conducting the business."
2.AdjectiveServing as an instrument, medium, means, or agency.
3.AdjectivePertaining to, made by, or prepared for an instrument, especially a musical instrument (rather than the human voice)."instrumental music; an instrumental part"
4.AdjectiveA pause in the vocals of a song, usually occurring midway through, in which a musical instrument replaces the vocals.
5.AdjectiveApplied to a case expressing means or agency, generally corresponding to the English use of prepositions such as by, with, through, or by means of with the objective case."the instrumental case"
6.NounThe instrumental case.
7.NounA composition written or performed without lyrics or singing, using a lead instrument to replace vocals.