The word Relapse is found in the Big Book 5 times,
Slip is mentioned 2 times.
There is no real distinction as far as I can tell by reading the contexts.
Interesting to note that under Slip we find Lapse
and under relapse we find to slip
In my opinion, any distinction is personal, and not based in fact or research.
From Webster:
Pronunciation:
\ˈslip\
Inflected Form(s):
slipped; slip·ping
Etymology:
Middle English slippen, from Middle Dutch or Middle Low German; akin to Middle High German slipfen to slide, Old High German slīfan to smooth, and perhaps to Greek olibros slippery
Date:
14th century
: to fall into error or fault : lapse
Main Entry:
1re·lapse Listen to the pronunciation of 1relapse Listen to the pronunciation of 1relapse
Pronunciation:
\ri-ˈlaps, ˈrē-ˌ\
Function:
noun
Etymology:
Middle English, from Medieval Latin relapsus, from Latin relabi to slide back, from re- + labi to slide — more at sleep
Date:
15th century
1 : the act or an instance of backsliding, worsening, or subsiding
2 : a recurrence of symptoms of a disease after a period of improvement
3 : to slip or fall back into a former worse state