There are plenty of epigraphic resources and resource lists accessible online that are of use to the seasoned epigraphist as much as to anyone just looking to decipher a seemingly cryptic epigraphic abbreviation. Some useful links are given below (in alphabetical order):

Abbreviations of Editions and Works of Reference for Alphabetic Greek Epigraphy

Digital Classicists EpiDoc project list

Epigraphy.info digital environment

Institute of Classical Studies OA-resource list (epigraphy & papyrology)

The Epigraphic Survey's digitalEPIGRAPHY