The noun expression has 9 senses (first 6 from tagged texts)
1. (23) expression, look, aspect, facial expression, face -- (the feelings expressed on a person's face; "a sad expression"; "a look of triumph"; "an angry face")
2. (18) expression, manifestation, reflection, reflexion -- (expression without words; "tears are an expression of grief"; "the pulse is a reflection of the heart's condition")
3. (15) expression, verbal expression, verbalism -- (the communication (in speech or writing) of your beliefs or opinions; "expressions of good will"; "he helped me find verbal expression for my ideas"; "the idea was immediate but the verbalism took hours")
4. (6) saying, expression, locution -- (a word or phrase that particular people use in particular situations; "pardon the expression")
5. (4) formulation, expression -- (the style of expressing yourself; "he suggested a better formulation"; "his manner of expression showed how much he cared")
6. (4) formula, expression -- (a group of symbols that make a mathematical statement)
7. expression -- ((genetics) the process of expressing a gene)
8. construction, grammatical construction, expression -- (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")
9. expression -- (the act of forcing something out by squeezing or pressing; "the expression of milk from her breast")