This Yiddish term is typically used when addressing a baby or small child. The English equiv. might be, "sweetie" or "babes" or something to that affect. Same as with English, this term can also be used between couples, a man might refer to his woman as, "bubula" or vice versa.
crying baby: wah wah
mamma: oh, bubula, don't cry
man: can I get you a drink, bubula?
woman: no you may not, and I'm not your bubula!
things such as sweetheart, darling, man, woman, couple, dear, babe, cutie, precious, special, lovey, dearist, pumpkin, angel, muffin, cupcake, boo, adorable or any other term of endearment!!
Nicole you are my BUBULA!!