In medicine|lang=en terms the difference between antiaggregant and anticoagulant

is that antiaggregant is (medicine) that prevents the aggregation of platelets; antiplatelet while anticoagulant is (medicine) a substance that prevents coagulation; that is, it stops blood from clotting.

As adjectives the difference between antiaggregant and anticoagulant

is that antiaggregant is (medicine) that prevents the aggregation of platelets; antiplatelet while anticoagulant is acting as an anticoagulant.

As a noun anticoagulant is

(medicine) a substance that prevents coagulation; that is, it stops blood from clotting.