Definition: force ink or metal on to (a surface) through a prepared screen of fine material so as to create a picture or pattern.
Screen printing is a printing technique where a mesh (screen) is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil (emulsion). A blade (squegee) is moved across the screen to fill (flood) the open mesh apertures with ink, and a reverse stroke then is used to push (print) the ink through the mesh and onto the substrate (t-shirt).
Each individual color is printed at a time, so several screens can be used to produce a multicolor image or design. Dark substrates require a white underbase for bright colors.