Coagulate \Co*ag"u*late\, v. t. [imp. & p. p. {Coagulated}; p. pr. & vb. n. {Coagulating}.] To cause (a liquid) to change into a curdlike or semisolid state, not by evaporation but by some kind of chemical reaction; to curdle; as, rennet coagulates milk; heat coagulates the white of an egg.