Webster's English Dictionary

expression

ex.pres.sion \ik-'spresh-*n\ \-'spresh-n*l, -*n-*l\ n 1a: an act, process, 
   or instance of representing in words or some other med ium : UTTERANCE 1b1: 
   something that manifests, embodies, or symbolizes something else  1b2: a 
   significant word or phrase  1b3: a mathematical or logical symbol or a 
   meaningful combination of symbol s 1b4: the detectable effect of a gene; 
   also : EXPRESSIVITY  2a: a mode, means, or use of significant 
   representation or symbolism; es p : felicitous or vivid indication or 
   depiction of mood or sentiment 2b1: the quality or fact of being expressive 
    2b2: facial aspect or vocal intonation as indicative of feeling  3: an act 
   or product of pressing out  - ex.pres.sion.al aj