The Collaborative International Dictionary
Tightening pulley
Tighten \Tight"en\, v. t. [imp. & p. p. Tightened; p. pr. & vb. n. Tightening.] To draw tighter; to straiten; to make more close in any manner.
Just where I please, with tightened rein
I'll urge thee round the dusty plain.
--Fawkes.
Tightening pulley (Mach.), a pulley which rests, or is forced, against a driving belt to tighten it.