1. To spend insufficient time, money, etc., on something when more is needed: For the sake of being healthy, people should not skimp on exercise or sleep.
2. To work carelessly, rapidly, or to use poor material in the construction of something: Marina's roof is leaking because the contractor skimped on the quality of the materials he was using.

Too many dictionaries; especially, medical and scientific lexicons, are skimping on their definitions to such a degree that they are often too difficult for users to understand what the word entries actually mean.