pipe-coupling

from The Century Dictionary.

• noun A joint or piece for uniting two pipes so as to form a continuous channel, or for forming a junction between a pipe and another object.
• noun When a short, bent, or offset pipe is used to connect two pipes which are not in line, it is called an offset; if the pipes are at an angle to each other, such a coupling, used in place of an elbow, is called a bend; if the two pipes are side by side, it is called a return-bend.