Sentence:  Second, incomplete coding is especially problematic for chronic conditions. Good evidence suggests that hospitals <WSD>undercode</WSD> chronic diseases, such as diabetes mellitus and hypertension, particularly for acutely ill pateints (Iezzoni et al. 1992; Jencks et al. 1988; Jollis et al. 1993; Malenka et al. 1994). 
Meaning of the word marked with <WSD> tags:  To use fewer codes than are needed to fully describe something.