The Collaborative International Dictionary of English v.0.48:

Deed poll \Deed" poll`\ (Law)
   A deed of one part, or executed by only one party, and
   distinguished from an indenture by having the edge of the
   parchment or paper cut even, or polled as it was anciently
   termed, instead of being indented. --Burrill.
   [1913 Webster]

WordNet (r) 3.0 (2006):

deed poll
    n 1: a deed made and executed by only one party

Bouvier's Law Dictionary, Revised 6th Ed (1856):

DEED POLL, contracts. A deed made by one party only is not indented, but
polled or shaved quite even, and is, for this reason, called a deed poll, or
single deed. Co. Litt. 299, a.
     2. A deed poll is not, strictly speaking, an agreement between two
persons; but a declaration of some one particular person, respecting an
agreement made by him with some other person. For example, a feoffment from
A to B by deed poll, is not an agreement between A and B, but rather a
declaration by A addressed to all mankind, informing them that he thereby
gives and enfeoffs B of certain land therein described.
     3. It was formerly called charta de una parte, and, usually began with
these words, Sciant praesentes et futuri quod ego A, &c.; and now begins,
"Know all men by these presents, that I, A B, have given, granted, and
enfeoffed, and by these presents do give, grant and enfeoff," &c. Cruise,
Real Prop. tit. 32, c. 1, s. 23.