olemus
(a) andmete laadimine ühest kohalikust seadmest teise,
eeskätt laua- või sülearvutist mobiilseadmesse,
näiteks USB, WiFi, mälukaardi vms kaudu
(b) Androidil = APK-vormingus rakenduspaketi installimine

Wiktionary:
sideload, verb
1. (transitive, computing) to transfer data between two local devices, rather than to or from a remote device
2. (transitive, computing) to install an app on a mobile device by using unofficial channels, such as avoiding the use of an app store by obtaining it directly from the developer or downloading from a software repository

ülevaateid
https://en.wikipedia.org/wiki/Sideloading