In science, it is defined as anything that is made of particles; and has rest mass and that occupies space (volume).
In general, it is the substance which composed the tangible objects. The objects or matter are consist of atoms which has a nucleus of protons and neutrons and an electron cloud. There are particles having neither rest mass nor volume like photons having are not considered matter. But not all particles with mass have a standard volume such as leptons and quarks. They are considered point particles when together can make up an ordinary matter.
Matter generally exists in 4 phases or states (solid, liquid, gas and plasma). Advances in science have revealed other phases such as the Bose-Einstein condensates, fermionic condensates, and quark-gluon plasma.