A few dictionaries were pilfered for their defintions of colloquial. Here's what they had to say.
col-lo'qui-al
/k&-lO'kwE-&l/
adj.
Abbr. coll., colloq.
1.
Charateristic of or appropriate to the spoken language or to
writing that seeks its effect; informal in diction or style of
expression.
2.
Relating to conversation; conversational [From
COLLOQUY].
col-lo'qui-al-ly adv.
col-lo'qui-al-ness n.
The American Heritage Dictionary of the English Language. 1980.
col-lo'qui-al a. Pertaining to, or used
in, conversation, esp. common and familiar conversation;
conversational;
hence, unstudied;
informal;
as, colloquial intercourse;
colloquial phrases;
colloquial style.
col-lo'qui-al-ly adv.
His [Johnson's] colloquial talents were, indeed, of
the highest order. Macaulay.
Webster Dictionary. 1913.
col-lo-qui-al
/k&-'lO-kwE-&l/
adjective.
1.
of or relating to conversation : CONVERSATIONAL
2.
a. used in or characteristic of familiar and informal conversation;
also : unacceptably informal
b. using conversational style.
colloquial noun;
col-lo-qui-al-i-ty /-"lO-kwE-'a-l&-tE/ noun;
col-lo-qui-al-ly /-'lO-kwE-&-lE/ adverb.
Merriam-Webster OnLine:
WWWebster Dictionary. 1998.
http://www.m-w.com/dictionary.htm
(21 January 1999).