plural of Penning trap

A colonial marine cnidarian of the order Pennatulacea.

plural of pen pencil

(India) mechanical pencil

An instrument for drawing geometric curves, in which the movements of a pen or pencil attached to a revolving arm of adjustable length may be indefinitely varied by changing the toothed wheels which give motion to the arm.

plural of Penning gauge

A kind of cold-cathode ionization gauge.

plural of pen shell

Any of the Pinnidae, a family of large saltwater clams.

A ballpoint pen.