Yes, APPLICATION is a Scrabble word!

Letter values in Scrabble US: A 1, P 3, P 3, L 1, I 1, C 3, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

APPLICATION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the act of bringing something to bear; using it for a particular purpose
a verbal or written request for assistance or employment or admission to a school
the work of applying something;
a program that gives a computer instructions that provide the user with tools to accomplish a task
liquid preparation having a soothing or antiseptic or medicinal action when applied to the skin
a diligent effort
the action of putting something into operation

Also: practical application, application program, applications programme.