A zip fastener.

A fastener used in clothing, bags, etc, comprised of two rows of teeth that are made to fit into each other by moving a slider along their length and opened again by moving the slider in the other direction.

Excessively particular, demanding, or fussy about details, especially about tidiness and cleanliness. / Overly concerned about tidiness and cleanliness. / Difficult to please; quick to find fault.

Something or someone that fastens. / Mechanically, any device that fastens; especially, a collective term for items such as screws, nuts, washers, clasps, bolts and the like.

simple past tense and past participle of fasten

(baseball) A pitch thrown with an offset grip and a moderate amount of added pressure by middle finger yielding a combination of backspin and some sidespin, resulting in motion to the left when thrown by a right handed pitcher with velocity only slightly diminished from that of a fastball

(baseball) Any of the variations of high speed pitches thrown in baseball

(baseball) A pitch thrown with a grip in the "horseshoe" orientation of the ball, with the rotation at a slight angle resulting in less Magnus effect as compared to a four-seam fastball since only two of the ball's seams cross the flight path; the pitch is delivered with a similar velocity as a four-seam fastball, but has a degree of sink.

(baseball) A moderate rotation speed backspin pitch thrown with a ball gripped between the index finger and middle finger; it has good velocity, may have a precessing spin, and sinks as it approaches the plate.

(baseball) A backspin pitch thrown with a ball gripped in the direction to cause four of the seams of the ball to cross the flight path and released with roughly equal pressure by the index and middle fingers