concrescence
noun
con·cres·cence kən-ˈkre-sᵊn(t)s 
kän-
1
: increase by the addition of particles
2
: a growing together : coalescence
concrescent
kən-ˈkre-sᵊnt
adjective kän-
Word History
Etymology
borrowed from Latin concrēscentia "coagulation, solidification," noun derivative of concrēscent-, concrēscens, present participle of concrēscere "to coalesce, condense, solidify, harden," from con- con- + crēscere "to come into existence, increase in size or numbers" — more at crescent entry 1
First Known Use
1614, in the meaning defined at sense 1
Medical Definition
concrescence
noun
con·cres·cence kən-ˈkres-ᵊn(t)s, kän-
: a growing together : coalescence
especially : convergence and fusion of the lateral lips of the blastopore to form the primordium of an embryo