Miniaturization was the process of making something smaller using modern technology. Another meaning for it was shrinking in size.
The subspace compression anomaly discovered by Starfleet in 2374 created severe spatial distortion, including miniaturization. (DS9: "One Little Ship")
Kathryn Janeway asked The Doctor if he had used USS Voyager's replicators to create the miniaturized souvenir copies of himself for the Qomar. He explained that he hadn't, but rather the Qomar were creating them at a holo-processing plant. (VOY: "Virtuoso")