Definition from Wiktionary, the free dictionary
- IPA: /ˌzuːm ˈɪn/
- (intransitive) To focus a zoom lens in order to obtain a larger image, or a closer view.
- (intransitive) To manipulate a display (such as a computer screen) so as to make it larger and possibly more detailed.
See also 
to focus a zoom lens in order to obtain a larger image
to manipulate a display so as to make it larger