<p><strong>Noun</strong></p><ul><li>the rear part of the human body, extending from the neck to the lower end of the spine</li><li>the part of the body of animals corresponding to the human back</li><li>the rear portion of any part of the body</li><li>the whole body, with reference to clothing</li><li>ability for labor; effort or strength</li><li>the part opposite to or farthest from the front; the rear part</li><li>the part that forms the rear of any object or structure</li><li>the area directly behind a person</li><li>the part that covers the back</li><li>the spine or backbone</li><li>any rear part of an object serving to support, protect, etc.</li><li>Nautical, Aeronautics. the forward side of a propeller blade</li><li>the top part or upper surface of an aircraft</li><li>Bookbinding. the edge of a book formed where its sections are bound together</li><li>the backs, grounds along the River Cam in back of certain colleges at Cambridge University in England</li><li>Architecture. extrados</li><li>Carpentry. the upper side of a joist, rafter, handrail, etc.</li><li>Mining. the roof of a stope or drift</li><li>Sports. a player whose regular position is behind that of players who make initial contact with the opposing team</li></ul><p><strong>Verb</strong></p><ul><li>to support, as with authority, influence, help, or money</li><li>to bet on</li><li>to cause to move backward</li><li>to furnish with a back</li><li>to lie at the back of; form a back or background for</li><li>to provide with an accompaniment</li><li>to get upon the back of; mount</li><li>to write or print on the back of; endorse; countersign</li><li>Carpentry. to attach strips of wood to the upper edge of (a joist or rafter) to bring it to a desired level</li><li>Nautical. to alter the position of (a sail) so that the wind will strike the forward face</li><li>to brace (yards) in backing a sail</li><li>to reinforce the hold of (an anchor) by means of a smaller one attached to it and dropped farther away</li><li>to go or move backward</li><li>Nautical. (of wind) to change direction counterclockwise (veer)</li></ul><p><strong>Adjective</strong></p><ul><li>situated at or in the rear</li><li>belonging to the past</li><li>in arrears; overdue</li><li>coming or going back; moving backward</li></ul><p><strong>Verb Phrase</strong></p><ul><li>to abandon an argument, opinion, or claim; withdraw; retreat</li><li>to retreat; withdraw</li><li>to back down</li></ul><p><strong>Textiles</strong></p><ul><li>to reverse (the spindle) in mule spinning prior to winding on the newly spun length of yarn</li></ul><p><strong>Computers</strong></p><ul><li>to duplicate (a file or a program) as a precaution against failure</li><li>to fail to keep an engagement or promise; withdraw from; abandon</li></ul>