noun one who expends money extravagantly, viciously, or without necessity; one that is profuse or lavish in any expenditure; a waster; a spendthrift.
2. prodigal ·adj given to extravagant expenditure; expending money or other things without necessity; recklessly or viciously profuse; lavish; wasteful; not frugal or economical; as, a prodigal man; the prodigal son; prodigal giving; prodigal expenses.