Full Idea
A set is 'effectively enumerable' if an (idealised) computer could be programmed to generate a list of its members such that any member will eventually be mentioned (even if the list is empty, or without end, or contains repetitions).
Gist of Idea
A set is 'effectively enumerable' if a computer could eventually list every member
Source
Peter Smith (Intro to Gödel's Theorems [2007], 02.4)
Book Reference
Smith,Peter: 'An Introduction to Gödel's Theorems' [CUP 2007], p.15