Definitions for overbuyˌoʊ vərˈbaɪ
Random House Webster's College Dictionary
o•ver•buyˌoʊ vərˈbaɪ(v.)-bought, -buy•ing.
(v.t.)to purchase in excessive quantities.
(v.i.)to buy regardless of one's needs or financial means.
Origin of overbuy:
1400–50; late ME overbiggen
To buy excessively, especially to buy more than one needs or can afford.