BE UNTHRIFTY is an idiom that means to be wasteful or extravagant with money. It is often used as a warning against spending too much money on unnecessary items. The crossword solutions for this term are SPEND, which is the act of using money to purchase goods or services, and THRIFTY, which is the practice of being careful with money and avoiding waste. Together, these two words form the phrase BE UNTHRIFTY, which is a warning against spending too much money.