An individual with blood type O receives type A blood. The phenomenon is agglutination.

Can explain more?

2 answers

Since this is not my area of expertise, I searched Google under the key words "agglutination blood" to get these possible sources:

http://www.google.com/search?client=safari&rls=en&q=agglutination+blood&ie=UTF-8&oe=UTF-8

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
RBC's of type O do not have surfarce antigens; in the blood of this individual will be naturally occuring antibodies to A type antigens on RBC's of the donor. Reaction between anti-A antobodies with A antigens in the donor's blood will cause type II hypersensitivity reaction leading to RBC (red blood cell) lysis.