1) connections 2) fittings 3) pipe fittings 4) line fittings the leakproof devices to connect pipelines to one another, or to equipment GRM: pl.n. (1,2,3,4) REG: Canadian English (4) Note: examples of fittings: short pipes (nipples), couplings, elbows, unions, tees, flanges, swages, used to make up a system of piping