It looks to me as if all the interested parties have been heard from, so here's the scoop:

UMAMI might be ( -- barring clerical error in my part):

a) the distaff side of an Imam's family
-- submitted by consuelo
-- chosen by Jackie

b) Gullah word for soul
-- submitted by TEd Remington
-- chosen by Elizabeth Creith, AnnaStrophic, themilum and (with some cajoling) Alex Williams

c) (chiefly veterinary) state of excitation or increased metabolism preceding labor -- submitted by Alex Williams

d) a philosophical concept in Islam in which the parts of a whole are distinct and have their own complete being apart from the whole they compose
-- submitted by Father Steve
-- chosen by themilum at first, but he reconsidered

e) a short shift, or wrap-around dress
-- submitted by belMarduk
-- chosen by Ted Remington

f) African thumb piano made of 22 to 28 metal keys mounted on a hardwood soundboard; also known as mbira
-- submitted by AnnaStrophic

g) a cooked combination of ground mixed grains, made into small balls and dipped into sauces
-- submitted by Elizabeth Creith
-- chosen by belMarduk and WhitmanONeill

h) the fifth fundamental taste, after sweet, sour, salty, and bitter, sometimes called “savory;” identified in 1908 by the Japanese scientist Kikunae Ikeda
-- the real McCoy.
-- chosen by Owlbow.
See this link. I was surprised to learn it was that old! The paradigm of the taste is mono-sodium glutamate, marketed a while back as Ac’cent, and supposed to be the cause of what was in the late 1960s known as the “Chinese Restaurant syndrome.”

i) adj. SW US dialect: vacant as the wind
-- submitted by WhitmnONeill
-- chosen by tsuwm, consuelo

j) a West African dish made from lentils
-- submitted by Jackie
-- chosen by musick

k) a style of West African headdress
-- also submitted by Jackie and she changed it at my suggestion but I forgot to delete the original

l) the box-like device worn in the small of the back by geishas when dressed full kimono and obi
-- submitted by Faldage
-- chosen by Father Steve and Bingley

m) what the Ubangi answered when asked by an orangantangi the name of the only river that drains Lake Victoria in Ugandi
-- submitted by themilum

n) a deathbed promise to exact revenge
-- submitted by musick

o) Swahili word meaning "glorious"
-- submitted by etaoin
-- chosen by Faldage and etaoin

A shibbloeth shattered, or at least battered: the real definition sounds like an armil (see TEd Remington’s comment) and it’s neither short nor dictionary-sounding. At least it’s trying not to be.

Recognized in 1907! Imagine that! Ninety-nine years ago!

edit: Oops, Only 98 years ago. 1908. [Sosumi-sound-effect]