What is the meaning of Mwah?

The sound of a kiss, to indicate blowing a kiss to someone.

The hallmark sound of a fretless bass guitar played with a certain technique, where treble frequencies increase gradually after the attack.

meh

sibling-in-law; brother-in-law, sister-in-law

full of holes, worn out

and

also

even

emphatic particle

Source: wiktionary.org