slip by vs slip away

slip by and slip away both are verbs.

Word	Noun	Adjective	Verb	Adverb
slip by	No	No	Yes	No
slip away	No	No	Yes	No

As verbs, slip by and slip away are synonyms defined as:

Other synonyms of slip by include elapse, glide by, go along, go by, lapse, pass, slide by.

slip by (verb)	slip away (verb)
for time to move forward	for time to move forward
	leave furtively and stealthily