What is the meaning of M-?

Abbreviation of milli-.

murine; pertaining to mice

meta-

Alternative form of n- before labials

Non-productive expressive prefix.

forms masculine abstract nouns from verbs, with the resulting root structure /ˈmiCCiC/

forms agent nouns from verbs, with the resulting root structure /ˈmaCCaC/ or /mVCˈCiCVw/ if masculine and /maCˈCaːCit/ or /mVCˈCiCwVt/ if feminine

forms instrumental nouns from verbs, with the resulting root structure /ˈmaCCaC/ or /mVCˈCiCVw/ if masculine and /maCˈCaːCit/ or /mVCˈCiCwVt/ if feminine

forms passive nouns from verbs, with the resulting root structure /miˈCuːCiC/ if masculine and /miˈCuCCit/ if feminine

forms nouns from other nouns with no apparent change in meaning, with the resulting root structure unchanged but for the addition of /ma-/ and the loss of final -w in masculine nouns

forms nomina loci from verbs and nouns

you plural (used for conjugating verbs to the subjective or nominative case of the personal pronoun)

him, her, it; class 1 object concord; form of mu- used before stems of more than one syllable.

me

him, her, it; class 1 object concord; form of mu- used before stems of more than one syllable.

him, her, it; class 1 object concord; form of mu- used before stems of more than one syllable.

Marks a transitive verb as having a second-person agent/subject.

Marks an intransitive verb with agent-like argument as having a second-person argument/subject.

With following vowel lengthened if in an unreduced open syllable.

m class(I) noun prefix and adjective agreement prefix, denoting mostly people

Forms the name of somebody who does something, has a certain characteristic, or is from a certain place.

m class(III) noun prefix and adjective agreement prefix, denoting mostly plants and inanimate natural things

Forms the name of a plant from its fruit.

u class(XI) adjective agreement prefix

you, 2nd person plural subject concord

verb-initial form of -m- (her, him; 3rd person singular (m class(I)) object concord)

therein, mu class(XVIII) subject concord

n class(IX/X) noun prefix and adjective agreement prefix, including for plurals of some u class(XI) nouns, used before labial consonants

him, her, it; class 1 object concord.

Class 1 simple noun prefix; form of mu- used before stems of more than one syllable.

him, her, it; class 1 object concord; form of mu- used before stems of more than one syllable.

Class 3 simple noun prefix; form of mu- used before stems of more than one syllable.

Class 9 simple noun prefix; form of n- used before stems beginning with a labial consonant.

Source: wiktionary.org