Wiktionary
n. 1 (context mathematics English) monomial expressions whose variable components are identical. 2 (context mathematics English) algebraic expressions whose literal coefficients represent the same value regardless of the numbers assigned to them.
Wikipedia
In algebra, like terms are terms that have the same variables and powers. The coefficients do not need to match.
Unlike terms are two or more terms that are not like terms, i.e. they do not have the same variables or powers. The order of the variables does not matter unless there is a power. For example, 8xyz and −5xyz are like terms because they have the same variables and power while 3abc and 3ghi are unlike terms because they have different variables. Since the coefficient doesn't affect likeness, all constant terms are like terms.