n, often attrib  1  :  the rear end or a process or prolongation of the rear end of the body of an animal  2  :  one end of a molecule regarded as opposite to the head : esp  :  the end of a lipid molecule that consists of a nonpolar hydrocarbon chain and is opposite to the polar group <most surface-active agents have a long hydrophobic attached to a polar head -R. E. Kirk & D. F. Othmer>   3  :  any of various parts of bodily structures that are terminal: as  a  :  the distal tendon of a muscle  b  :  the slender left end of the human pancreas  c  :  the common convoluted tube that forms the lower part of the epididymis  4  :  the part of a sperm consisting of the middle portion and the terminal flagellum  5  :  a thin protein tube which forms part of the coat of some bacteriophages and through which DNA is injected into a cell tailed adj tail*less adj 
 
 
 
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