This term originated in the Netherlands during the Golden Age when the price of a tulip was greater than the income of the working class. Today, it refers to the time when investors let go of realistic expectations, leading to a price swelling of an asset or sector. This cycle inflates prices until investors realize the real worth of such assets and prices collapse causing many to go bankrupt.
Additional meaning of Tulipmania:
A recent example of Tulipmania is the dotcom bubble of the late 1990s.