The Collaborative International Dictionary of English v.0.48:

Borrower \Bor"row*er\, n.
   One who borrows.
   [1913 Webster]

         Neither a borrower nor a lender be.      --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

borrower
    n 1: someone who receives something on the promise to return it
         or its equivalent [ant: lender, loaner]

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

BORROWER, contracts. He to whom a thing is lent at his request.
     2. The contract of loan confers rights, and imposes duties on the
borrower' 1. In general, he has the right to use the thing borrowed, during
the time and for the purpose intended between the parties; the right of
using the thing bailed, is strictly confined to the use, expressed or
implied, in the particular transaction, and by any excess, the borrower will
make himself responsible. Jones' Bailment, 58 6 Mass. R. 104; Cro. Jac. 244;
2 Ld. Raym. 909; Ayl. Pand. B. 4, t. 16, p. 517; Domat, B. 1, t. 5, Sec. 2,
n. 10, 11, 12; Dio. 13, 6, 18 Poth. Pret a Usage, c. 2, Sec. 1, n. 22; 2
Bulst. 306; Ersk. Pr. Laws of ScotI. B. 3, t. 1, Sec. 9; 1 Const. Rep. So.
Car. 121 Bracton, Lib. 3, c. 2, Sec. l, p. 99. The loan is considered
strictly personal, unless, from other circumstances, a different intention
may be presumed. 1 Mod. Rep. 210;  S. C. 3 Salk. 271.
     3. - 2. The borrower is bound to take extraordinary care of the thing
borrowed; to use it according to the intention of the lender, to restore it
in proper time; to restore it in a proper condition. Of these, in their
order.
     4. - 1. The loan being gratuitous, the borrower is bound to
extraordinary diligence, and is responsible for slight neglect in relation
to the thing loaned. 2 Ld. Raym. 909, 916 Jones on Bailm. 65; 1 Dane's Abr.
c. 17, art. 12; Dig. 44, 73 1, 4; Poth. Pret. a Usage, c. 2, Sec. 2, art.
21, n. 48.
     5. - 2. The use is to be according to the condition of the loan; if
there is an excess in the nature, time, manner, or quantity of the use,
beyond what may be inferred to be within the intention of the parties, the
borrower will be responsible, not only for any damages occasioned by the
excess, but even for losses by accidents, which could not be foreseen or
guarded against. 2 Ld. Raym. 909; Jones on Bailm. 68, 69.
     6. - 3. The borrower is bound to make a return of the thing loaned, at
the time, in the place, and in the manner contemplated by the contract..
Domat, Liv. 1, t. 5, Sec. 1, n. 11; Dig. 13, 6, 5, 17. If the borrower does
not return the thing at the proper time, he is deemed to be in default, and
is generally responsible for all injuries, even for accidents. Jones on
Bailm. 70; Pothier, Pret a Usage , ch. 2, Sec. 3, art. 2, n. 60; Civil Code
Of Louis. art. 2870; Code Civil, art. 1881; Ersk. Inst. B. 3, t. 1, Sec. 22
Ersk. Pr. Laws of Scotl. B. 3, t. 1, Sec. 9.
     7. - 4. As to the condition in which the thing is to be restored. The
borrower not being liable for any loss or deterioration of the thing, unless
caused by his own neglect of duty, it follows, that it is sufficient if he
returns it in the proper manner, and at the proper time, however much it may
be deteriorated from accidental or other causes, not connected with any such
neglect. Story on Bailm. eh. 4, Sec. 268. See, generally, Story on Bailm.
oh. 4; Poth. Pret A Usage; 2 Kent, Com. 446-449; Vin. Abr. Bailment, B 6;
Bac. Abr. Bailment; Civil Code of Louis. art. 2869-2876; 1 Bouv. Inst. n.
1078-1090. Vide Lender.