Full Definition of FUND. 1. a: a sum of money or other resources whose principal or interest is set apart for a specific objective b: money on deposit on which checks or drafts can be drawn —usually used in plural c: capital d plural: the stock of the British national debt —usually used with the.2.. a: a sum of money or other resources whose principal or interest is set apart for a specific objective b: money on deposit on which checks or drafts can be drawn —usually used in plural c: capital d plural: the stock of the British national debt —usually used with the. 2.