Definitions for "mellowing"
The act or process of acquiring desirable qualities by being left undisturbed for some time.
having or suggesting softness and richness in quality; "a mellow sound"; "the mellow air brought in the feel of imminent autumn"- Thomas Hardy; "a mellowing sun"
What happens to a tobacco leaf's youthful character of time. In particular, Latakia leaf's unique flavors are said said to mellow over time.
Keywords:  becoming, process
the process of becoming mellow
pr. p. of mellow.