monkey vs mess around

monkey is a noun but mess around is not a noun.

Word	Noun	Adjective	Verb	Adverb
monkey	Yes	No	Yes	No
mess around	No	No	Yes	No

As verbs, monkey and mess around are synonyms defined as:

monkey and mess around: do random, unplanned work or activities or spend time idly

Other synonyms of monkey include monkey around, muck about, muck around, potter, putter, tinker.

monkey (noun)	mess around (noun)
any of various long-tailed primates (excluding the prosimians)
one who is playfully mischievous

monkey (verb)	mess around (verb)
do random, unplanned work or activities or spend time idly	do random, unplanned work or activities or spend time idly
play around with or alter or falsify, usually secretively or dishonestly