1. reduce something in number or size
thin out the options/crowd
To 'thin something out' means to reduce something or to make a group of things fewer in number. You might 'thin something out' by cutting down, reducing, trimming back, trimming down or cutting back something. You can 'thin out' soup for example by adding milk or water, in order to feed more people. You could 'thin out' hair or a plant that has been growing thickly. If you 'thin yourself out' you are spreading yourself broadly over a number of different tasks instead of concentrating on one task.