verb (used without object)
to transfer software, data, etc., from one local system or device to another, typically from one's computer to a mobile device.
verb (used with object)
to transfer (software, data, etc.) by this process: It'll take two more minutes to sideload my podcasts to my phone.
1995–2000; in the sense ‘off to the side’, i.e., not over the Internet; patterned after upload and download