muss
[noun]
Synonyms: brawl, broil, donnybrook, fracas, fray, free-for-all, knock-down-and-drag-out, melee, ruction, set-to, mess, botch, botchery, hash, mess-up, mix-up, muddle, mull, shambles

[TahlilGaran] English Synonym Dictionary ▲

I. muss¹ /mʌs/ (also muss up) verb [transitive] informal especially American English
[Date: 1800-1900; Origin: Probably from mess]
to make something untidy, especially someone’s hair:
Briscoe reached down and mussed the boy’s hair.

[TahlilGaran] Dictionary of Contemporary English ▲

II. muss² noun
no muss, no fuss used to say that something can be done easily and without problems – used humorously:
It works every time, no muss, no fuss.

[TahlilGaran] Dictionary of Contemporary English ▲