Sentence:  This meant , concretely , that the patient could not read at all without making writing like movements of the head or body , became easily confused by `` hasher marks '' inserted between hand-written <WSD>words</WSD> and thus confused the mark for one of the letters , and could recognize a simple straight line or a curved one only by tracing it . 
Meaning of the word marked with <WSD> tags:  a unit of language that native speakers can identify