Platelet Aggregation: is the clumping together of platelets in the blood to stop the blood from getting out of the body. For instance, if you cut yourself, soon enough, the blood stops because your body initiates platelet aggregation to clog up the cut to keep from blood loss!

Cited: Medterms.com. Updated 2006. Accessed 1 Dec 2006. http://www.medterms.com/script/main/art.asp?articlekey=33673