Merriam-Webster Collegiate Dictionary - back

 I. noun  Etymology: Middle English, from Old English b?c; akin to Old High German bah ~, Old Norse bak  Date: before 12th century  1.  a.  (1) the rear part of the human body especially from the neck to the end of the spine  (2) the body considered as the wearer of clothes  (3) capacity for labor, effort, or endurance  (4) the ~ considered as the seat of one's awareness of duty or failings get off my ~  (5) the ~ considered as an area of vulnerability the police officer's partner always watches his ~  b. the part of a lower animal (as a quadruped) corresponding to the human ~  c. spinal column  d. spine 1c  2.  a. the side or surface opposite the front or face ; the rear part; also the farther or reverse side  b. something at or on the ~ for support ~ of a chair  c. a place away from the front sat in ~  3. a position in some games (as football or soccer) behind the front line of players; also a player in this position  • ~ed adjective  • ~less adjective  II. adverb  Date: 14th century  1.  a. to, toward, or at the rear  b. in or into the past ; ~ward in time; also ago  c. to or at an angle off the vertical  d.  (1) under restraint  (2) in a delayed or retarded condition  2.  a. to, toward, or in a place from which a person or thing came  b. to or toward a former state  c. in return or reply  III. adjective  Date: 15th century  1.  a. being at or in the ~ ~ door  b. distant from a central or main area ~ roads  c. articulated at or toward the ~ of the oral passage ~ vowels  2. having returned or been returned  3. being in arrears ; overdue  4. moving or operating ~ward ; reverse  5. not current ~ issues of a magazine  6. constituting the final 9 holes of an 18-hole golf course  IV. verb  Date: 1548  transitive verb  1.  a. to support by material or moral assistance — often used with up  b. substantiate  c. to assume financial responsibility for  d. to provide musical accompaniment for — often used with up  2.  a. to cause to go ~ or in reverse  b. to articulate (a sound) with the tongue farther ~  3.  a. to furnish with a ~  b. to be at the ~ of  intransitive verb  1. to move ~ward — often used with up  2. of the wind to shift counterclockwise — compare veer  3. to have the ~ in the direction of something  Synonyms: see support, recede  • ~er noun BACK  geographical name river 605 miles (974 kilometers) Canada in Nunavut rising along border with Northwest Territories & flowing ENE into Arctic Ocean