rēˈājə̇n noun
( -s )
Etymology: International Scientific Vocabulary reag ent + -in
1. : a substance in the blood of persons with syphilis that is sometimes held to be an antibody and is responsible for positive Wassermann, Kahn, or other serological reactions for syphilis
2. : an antibody in the blood of individuals with atopic allergy that does not react visibly in vitro but possesses the power of passively sensitizing the skin of normal individuals
• re·agin·ic |rēə|jinik adjective
• re·agin·i·cal·ly -nə̇k(ə)lē adverb