Titties that are not high and firm, but instead, fleshy and pillowy soft. Usually only found on bigger girls or women who have had kids. Good for burying your face in and getting lost; so-so good for tittie fucking.
Note: 'Mellow melons is a combo of the words "marshmellow" and "melons". It does not mean her tits are mellow as in 'chilled out'.
Donna has some nice 'mellow melons. It's like squeezing clouds.