methylphenidate Syllabification: (meth·yl·phen·i·date)Pronunciation: /ˌmeTHəlˈfenəˌdāt/Definition of methylphenidate noun Medicine a synthetic drug that stimulates the sympathetic and central nervous systems and is used to improve mental activity in attention deficit disorder and other conditions. methylphenidate in other Oxford dictionaries Definition of methylphenidate in the British & World English dictionary