1) Plastering between tiles 
• (p. pr. & vb. n.) of Grout • (n.) The process of filling in or finishing with grout; also, the grout thus filled in.
(from the article `tunnels and underground excavations`) ...could result in up to 5 percent lost ground, an amount intolerable in urban work. Lost ground is held to reasonable levels by promptly blowing ... ...concrete lining. Excavation is by drilling and blasting with muck loaded into large buckets, with larger shafts operating four b...
Grouting is the process of filling the gaps between tiles with grout - to ensure a waterproof finish.
The operation of introducing a binder into the interstices of a material in situ under the action either of gravity or applied pressure.
Grout'ing noun The process of filling in or finishing with grout; also, the grout thus filled in. Gwilt. 
The process of sealing off a water flow in rocks by forcing a thin slurry of cement or other chemicals into the crevices; usually done through a diamond drill hole.