It is not a brand name, it means that the size of the clothes is M.

medium?

1. Pronunciation: British ['mi?di?m] American ['mi?di?m]

2. Meaning: adj . Medium; moderate

n. Means; medium; media

3. Used as an adjective (adj.)

The blue cap is a medium size .

The blue hat is the medium size.

4. Used as a noun (n.)

Commercial television is an effective medium for advertising.

Commercial television is an effective advertising tool.

Extended information

Synonyms:

average　?

Pronunciation: English ['?v?r?d?] American [ '?v?r?d?]

Meaning: n. average; average level

adj. average; general; usual

v . Take the average; reach the average level

Example:

The average age of the boys in this class is fifteen.

The average age of the boys in this class is fifteen. Fifteen years old.

Tom's work at school is above the average.

Tom's work at school is above the average.

Tom's work at school is above the average.