noun / verb
cap
KAP/kæp/
A covering fitted over a top or opening.
The soft cap has a curved brim projecting from its crown.

Etymology
Cappa's head-covering sense survives in the hat; by resemblance, cap also came to mean a fitted covering for an object's end or opening. The deeper origin of cappa is uncertain.
In context
if I unscrew this plastic cap up here that comes off
More examples
- He pulls his wool cap over his ears.
- The agreement caps annual rent increases.
- The clinician explains how a contraceptive cap covers the cervix.
Forms
cap · caps · capped · capping