Definitions for "deixis"
the function or operation of a deictic word; the function of pointing or specifying from the perspective of a participant in an act of speech or writing; aspects of a communication whose interpretation depends on knowledge of the context in which the communication occurs.
This refers to words that take their meaning from their situation or the text around them. These can be words used for individuals for example pronouns, as in: Where is John? haven't seen him. They can be words used for places, as in: I'd love to go to Paris. I've already been there. They can be words used for times, as in: Can we meet at five on Monday? I've already got something then. I didn't do it yesterday, and I won't be doing it tomorrow. - where the words 'yesterday' and 'tomorrow' can only make sense in relation to when the speaker is speaking - 'today'. Other examples: Put your hands on your head I can't do it - where 'do it' can only make sense in relation to the command that preceded it. Have you seen that they've released that child-molester after six months? It's a scandal. (i.e. that she was released so early is a scandal)
A term used to refer to the context-boundedness of language. The deictic aspects of linguistics mesage are those elements that refer to time, space and the interpersonal components. Purely deictic segments in English are 'here/there', 'that/this', 'before/after/now' etc etc.