Same thing it means in normal English. Delayed until later.
Steinitz - 1.e4 e5 2.Nf3 Nc6 3.Bb5 d6
Deferred Steinitz - 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 d6
Alapin - 1.e4 c5 2.c3
Deferred Alapin - 1.e4 c5 2.Nf3 e6 3.c3
Etc
Same thing it means in normal English. Delayed until later.
Steinitz - 1.e4 e5 2.Nf3 Nc6 3.Bb5 d6
Deferred Steinitz - 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 d6
Alapin - 1.e4 c5 2.c3
Deferred Alapin - 1.e4 c5 2.Nf3 e6 3.c3
Etc
Ok, I thought it had to do with respecting your superiors or something. Like in the phrase, "I defer to you" meaning you agree to follow (someone else's decision, a tradition, etc.).
"The Monkey's Bum Deferred is a more respected variation in which White develops their queen's knight before playing Bc4 and Qf3." - https://en.wikipedia.org/wiki/Modern_Defense,_Monkey%27s_Bum
For example, this opening.