Well this is the definition I found on okizeme because I'm too stupid to word it myself lol. I honestly don't know how to describe it myself but I can see it when it happens
In general, Okizeme begins when a player knocks their opponent off of their feet. While on the ground, the opponent has several possible options (depending upon the game) including just getting up, rolling away/towards before getting up, rising with an attack, or a combination (i.e. rolling away/towards and rising with an attack). The player still standing will attempt to attack the opponent usually by countering their rising attack, allowing them to combo their opponent or, preferrably, knock them over again, thus keeping their advantage. In addition, the opponent does not react in time, the standing player can attack their opponent with a pounce attack, or certain types of low attacks for additional damage.
In most 2D Fighting Games, because the grounded opponent cannot be attacked, and/or can immediate counter or block any attempted attacks, Okizeme is more often used to make the opponent block or behave in a certain way. For example, the standing player throws a fireball so the opponent will get up into it, forcing them to either block it or get hit, which is guaranteed damage either way.
Watch this Millia match video (there's a Slayer mirror in the middle then it's Millia vs. Slayer) and what she does when Sol and Slayer are knocked down. THAT is okizeme. Sorry about the off-topicness ;____;
http://www.youtube.com/watch?v=casIuor98UE