Definitions for abcs
rudiment, first rudiment, first principle, alphabet, ABC, ABC's, ABCs(noun)
the elementary stages of any subject (usually plural)
"he mastered only the rudiments of geometry"
Kernerman English Learner's Dictionary
ABCs(noun)əˌbri viˈeɪ ʃən
Do you know your ABCs?
Letters, writing, especially as a skill.
He was busy learning his ABCs.
The alphabet, especially the English alphabet.