From WordNet (r) 1.6 [wn]:

  expression
       n 1: the expression on a person's face; "a sad expression"; "a
            look of triumph"; "an angry face" [syn: {look}, {aspect},
             {facial expression}, {face}]
       2: expression without words; "tears are an expression of
          grief"; "the pulse is a reflection of the heart's
          condition" [syn: {manifestation}, {reflection}, {reflexion}]
       3: the communication (in speech or writing) of your beliefs or
          opinions; "expressions of good will"; "he helped me find
          expression for my ideas"
       4: a word or phrase that particular people use in particular
          situations; "pardon the expression" [syn: {saying}, {locution}]
       5: the style of expressing yourself; "he suggested a better
          formulation"; "his manner of expression showed how much he
          cared" [syn: {formulation}]
       6: a group of symbols that make a mathematical statement [syn:
          {formula}]
       7: a group of words that form a constituent of a sentence and
          are considered as a single unit; "I concluded from his
          awkward constructions that he was a foreigner" [syn: {construction}]

In Drexler's view of knowledge enhancement and evolution a human being's capability to learn and know can be accelerated if the process by which knowledge or information is expressed is accelerated.