beta abstraction

from The Free On-line Dictionary of Computing (8 July 2008)

beta abstraction

   [{lambda-calculus}] The conversion of an expression to an
   {application} of a {lambda abstraction} to an argument
   expression.  Some subterm of the original expression becomes
   the argument of the abstraction and the rest becomes its
   body. E.g.

   	4+1 --> (\ x . x+1) 4

   The opposite of beta abstraction is {beta reduction}.  These
   are the two kinds of {beta conversion}.