A shortened version of "fiend" as in to fiend for something, jonesing, jonesin' etc. Usually when so desperate for addictive substance that the "feen" or person "feening" doesn't have time to complete the pronounciation of words, let alone entire sentences. Abbreviated for fiend.
FIEND:
1 a : DEVIL 1 b : DEMON c : a person of great wickedness or maliciousness
2 : a person
extremely devoted to a pursuit or study : FANATIC *a golf fiend*
3 : ADDICT 1 *a
dope fiend*
4 : WIZARD 3 *a fiend at
mathematics*
When I ran out of pot, I got crazy-like yo', I was
fiending... But now that I'm
addicted to crack, all I can ever do is run around all crazy-da-bomb like super-yo'! and feen, I'm like feenin'
all the time now...