WordNet sense 1 (a program that gives a computer instructions that provide the user with tools to accomplish a task):

application program, applications programme

WordNet sense 2 (liquid preparation having a soothing or antiseptic or medicinal action when applied to the skin):

lotion

WordNet sense 3 (the act of bringing something to bear; using it for a particular purpose):

practical application

WordNet sense 4 (the work of applying something):

coating, covering

WordNet sense 5 (a diligent effort):

diligence