pen

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A fenced enclosure for animals.
• noun The animals kept in such an enclosure.
• noun Any of various enclosures, such as a bullpen or playpen, used for a variety of purposes.
• noun A repair dock for submarines.
• transitive verb To confine in or as if in a pen. synonym: enclose.
• noun A female swan.
• noun A penitentiary; a prison.
• noun An instrument for writing or drawing with ink or similar fluid, especially.
• noun A ballpoint pen.
• noun A fountain pen.
• noun A pen point.
• noun A penholder and its pen point.
• noun A quill.
• noun An instrument for writing regarded as a means of expression.
• noun A writer or an author.
• noun A style of writing.
• noun Archaic Pinions.
• noun The chitinous internal shell of a squid.
• noun A pen shell.
• transitive verb To write or compose.

from The Century Dictionary.

• To shut, inclose, or confine in or as in a pen or other narrow place; hem in; coop up; confine or restrain within very narrow limits: frequently with up.
• To write; compose and commit to paper.
• noun A small inclosure, as for cows, sheep, fowls, etc.; a fold; a sty; a coop.
• noun Any inclousure resembling a fold or pen for animals.
• noun In the fisheries, a movable receptacle on board ship where fish are put to be iced, etc.
• noun A small country house in the mountains of Jamaica.
• noun A pen or pencil used to record the various degrees of pressure employed in writing. A metal spring, which holds the writing point of metal or graphite, plays against a rubber air-capsule contained in the penholder and connected by rubber tubing to the ordinary recording apparatus.
• noun A weir or dam for penning up the water in a stream, canal, or river of any kind, to form a head.
• noun An abbreviation of peninsula.
• noun A feather, especially a large feather, of the wing or tail; a quill.
• noun A quill, as of a goose or other large bird, cut to a point and split at the nib, used for writing; now, by extension, any instrument (usually of steel, gold, or other metal) of similar form, used for writing by means of a fluid ink.
• noun One who uses a pen; a writer; a penman.
• noun Style or quality of writing.
• noun 5. A pipe; a conduit.
• noun A female swan, the male being called a cob. Yarrell, British Birds.
• noun In Cephalopoda, an internal homogeneous corneous or chitinous structure replacing the internal shell in certain decacerous cephalopods, such as the typical squids (Loliginidæ): also called gladius and calamary: distinguished from the corresponding sepiost or cuttlebone of the cuttles. See cut under calamary.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To write; to compose and commit to paper; to indite; to compose.
• transitive verb To shut up, as in a pen or cage; to confine in a small inclosure or narrow space; to coop up, or shut in; to inclose.
• noun A small inclosure.
• noun Slang A penitentiary[6]; a prison.
• noun obsolete A feather.
• noun obsolete A wing.
• noun An instrument used for writing with ink, formerly made of a reed, or of the quill of a goose or other bird, but now also of other materials, as of steel, gold, etc. Also, originally, a stylus or other instrument for scratching or graving.
• noun Fig.: A writer, or his style.
• noun (Zoöl.) The internal shell of a squid.
• noun (Zoöl.), Prov. Eng. A female swan; -- contrasted with cob, the male swan.
• noun See Bow-pen.
• noun a pen for drawing dotted lines.
• noun a pen for ruling lines having a pair of blades between which the ink is contained.