1) Affectedly mellow and rich 2) Desirable 3) Very desirable 1) Desirable 
• (a.) Of the nature of a plum; desirable; profitable; advantageous.
Plum'my adjective [ From Plum .] Of the nature of a plum; desirable; profitable; advantageous. [ Colloq.] 'For the sake of getting something plummy .' G. Eliot. 
Plummy is British slang for rich, desirable.
Wines that taste of plums are usually round as well. Pomerol and St. Emilion produce plumy wines.
[adj] - (informal) `a plummy leading role` 2. [adj] - of a voice
adjective (of a voice) affectedly mellow and rich; `the radio announcer`s plummy voice`
Rich, concentrated wines can often have the smell and taste of ripe plums. When they do, the term plummy is applicable.