In your own words define materials science?

(My definition)
Materials Science is an interdisciplinary subject, spanning the physics and chemistry of matter, engineering applications and industrial manufacturing processes. 

(Google definition)
Definition of materials science. : the scientific study of the properties and applications of materials of construction or manufacture (as ceramics, metals, polymers, and composites)

both are kinda the same but mine sounds better and has understanding details

Metals, mixtures of metals = alloys, carbon atoms as in polymers, carbon as in graphite, diamond, graphene, and the science of these things in terms of their strengths, heat capacities, magnetic properties and "uncle tom cobbleigh and all" - ie everything else you can think of !