Cos'è trimmer? Cos'è trimmer? One that trims: a window trimmer. A device or machine, such as a lumber trimmer, that is used for trimming.One who changes one's opinions, especially in politics, to suit the needs of the moment.Electronics A variable component used to make fine adjustments to capacity or resistance.Architecture A beam across an opening, such as a hearth, into which the ends of joists can be fitted.