I’ve always understood it to mean “my dearest” and so I’ve taken to calling my special someone ‘bienamada’ - but I’m wondering if any native Spanish speakers can give me a more expanded definition of the word, if there is one. Also…is this a slang? colloquial?
Tibs.
IANAS(panish speaker), but Bienamada was the name of a really good horse, IIRC.
I’m not aware of any slang meaning but just looking at bienamada I’d say it’s actually 2 words bien and amada and literally it means “well loved”, referring to a female.
I think ‘bienamama’ means “yo mama’s good”
If that’s any help
“oh, bienamada, yo no te amaria!
En tu abrazo yo abrazo lo que existe,
la arena, el tiempo, el arbol de la lluvia,”
translates as
“oh, my dearest, I could not love you so!
But when I hold you I hold everything that is –
sand, time, the tree of the rain,”
from 100 Love Sonnets (Cien sonetos de amor) by Pablo Neruda
I would just go with the Gomez Addams line and call her “Querida” – “Beloved.”
Of course, this should be followed by kissing her starting at her hand and working your way up her arm to her lips.
hmmm…
mi cielo (translates - my sky) sounds nice 
-T