What is the meaning of Muss?

To rumple, tousle or make (something) untidy.

A mess (disagreeable mixture or confusion of things; disorder).

A scramble, as when small objects are thrown down, to be taken by those who can seize them; a confused struggle.

A term of endearment.

first/third-person singular present of müssen

first/second/third-person singular present indicative of mussen

Source: wiktionary.org