I think you mean "acidosis":) It's really difficult to make a "dummy" version of the definition. But acidosis is when the body's pH level drops below 7.35 If you want a good book that explains all this I suggest "Fluids & Electrolytes made Incredibly Easy"
Now I feel weird... but I liked A&P It may seem like a lot of work but stick with it. If you don't get all A's so what... your doing your best. Just because you can't remember all of the cranial nerves doesn't mean that you won't make a great nurse.