Replicators
Concept · Stellaris 4.5.2
Replicators in the Stellaris encyclopedia: Replicators turn Alloys into new Machine Pops.
Replicators in the game's words
The encyclopedia entry as the game shows it in its tooltips; underlined words open their own entry or page here.
Replicators turn Alloys into new 
Machine Pops.
A machine that builds a machine that builds a machine that...
Source: common/game_concepts (concept_replicator) and localisation/english, Stellaris Cygnus v4.5.2 (9776).