adjective
mellower; -est
[also more ~; most ~]
pleasantly rich, full, or soft :not harsh, bright, or irritating
having a pleasing rich flavor that develops over time
very calm and relaxed
b informal :relaxed from drinking alcohol or using drugs
verb
-lows; -lowed; -lowing
to become or to cause (someone or something) to become less harsh, irritating, nervous, etc. [no obj]
mellow out
[phrasal verb] US informal :to become relaxed and calm