I wanted to make a list lookup on another sitecollection or webapplikation - how can I do it?
Please check the below discussion
Does the reply from Aditya resolve your query? If yes, please mark it as correct answer.
Were you looking to do this on a Nintex form or from within a workflow?
I needed to make the lookup from list columm and use it in a form (from one site Collection https://infonet..... to https://intranet...) - both own by my orgnization.
(nintex 2013 enterprese)
From a form (2013 on-premise)
Maybe you can think on using Content Type Hub to share this column between Site Collections.