a solid: A favor.
Example: Do me a solid and send me that website link.

a whole 'nother: An entirely different. I've noticed this phrase in the vocabulary of many people of various backgrounds and have even heard it on national TV, but I have yet to see it written down (before now).
Example: That's a whole 'nother story.

A's and C's: n. (plural) abbr. of Arts and Crafts. Slang form, creative endeavour.
Example: They're letting me out of that place today so I can do some A's and C's.

A'stake: A mistake, (Thanks, Erin.)
Example: I'm sorry, I made a'stake.

A-Bag: Real estate exchanger term meaning a keeper property that would not be traded off without a substantial advantage gained.
Example: That's a good property--it's A-Bag.

A-D-orable: Really adorable and cute.
Example: Look at that guy, he's A-D-orable!

a-delic: Usually seen after funk, mack, or shag. Emphasizes the previous word to its maximum.
Example: That lowrider is pimp-a-delic.

a-dollar-three-eighty: The price for anything.
Example: Question: How much is it? Answer: A-dollar-three-eighty.

a-game: To do your best effort possible in any endeavor, not just pertaining to sports.
Example: I didn't do to well on that test last week, next time I'm going to bring my A-game.

A-list: A mythical group of weblogs and personal sites (and their creators) who are simply Much Cooler Than You. It is worth noting that (a) no such list actually exists, (b) those who are on the list adamantly deny its existence, and (c) it is not the same as the Cabal. A-list is frequently used in a mocking manner by those who are not members.
Example: Oh, one link from kottke.org and now you go all A-list on us! OR You haven't seen this yet? All the A-listers linked to it.

a-loin: Used in the place alone. Especially leave me alone.
Example: I'm having a bad day, so just leave me a-loin.

A-madnay: (uh-mad-nay) From the French, un moment donne, at a given time.
Example: We really need to catch up. Maybe we could go for coffee a-madnay.

a-scared: Like afraid, but not as dramatic. Usually an adjective, but sometimes a verb.
Example: Oh, you a-scared me, I didn't know anyone was here.

A.R. three-eighty: An anal rententive person. A perfectionist.
Example: Ugh, look at how he constantly straightens his hair. What an A.R. three-eighty.

Aabar: To use sly, deceitful, or illegal tactics to occupy the first place in any ordered listing, esp. phone directories.
Example: You will have to aabar well to rank higher in the dictionary than this.

aaboos: Abuse. Brummie translation of the Welsh.
Example: You are aaboosing me, you naughty Welshman.

aaiight!: All Right! Used in times of intense emotion.
Example: Dad: Son, get in there and clean your room. Son: Aaiight!

aarqeunaamaaei: (Pronounciation: arch-ay-nay-mey) Used in the place of arch enemy. However, aarqeunaamaaei usually refers to political enemies.
(Plural: aarqeunaamaaeis)
Example: Fidel Castro and George W. Bush are aarqeunaamaaeis.

Aazing: Like amazing, but not quite.
Example: The 30-story building was aazing.

abacoral: The backbone of a snail.
Example: Hello, class. We're going to look for abacorals today.

Abal: Used by the younger generation to label a person as dumb, uncouth, unsophisticated.
Example: You're just an Abal.

abbamatically: The tendency for an unbearably cloying song to
repeat over and over in your head all day after hearing it on the radio.
Example: More Than a Woman has been playing abbamatically in my head since breakfast.

abbeverate: To feed a person a drink, to offer a drink, or provide a drink.
Example: I'm going to abbeverate our guests before they die of thirst.

Abdicate: To give up all hope of ever having a flat stomach.
Example: If you drink 24 beers a day you must be prepared to abdicate seeing your toes again.

abeer: used in place of ahmen, usually as a type of thanks.
Example: Paul-I'll get the next round of sodas. Group (in unision)-abeer!

abella: Someone who owns everything possible.
Example: That abella rules at Counter-strike.

Aberzombie: One who wears only Abercrombie & Fitch clothing.
Example: Trust me, you're not his type. He's only into other Aberzombies like himself.

abnatural: an obscene violation of what is natural.
Example: McDonald's food, industrial pollution, and repression of happiness are all abnatural, screaming contradictions to healthy existence.

abode: A board. A piece of lumber used to build a structure.
Example: Is that abode fence?

aboot: About. Used to emphasize Canadianess.
Example: You're Canadian?
What are you talking aboot, eh?