Sentence:  The following week he wrot her. 'It is a most shameful thing that he should keep me on like this...I am awfully cross because now I am not able to come home for an <WSD>absit</WSD> [overnight leave] on Thursday which I very much wanted to do.' 
Meaning of the word marked with <WSD> tags:  Formal permission to be away from a college for the greater part of the day or more.