to throw violently into the air; especially, to throw (a frog) into the air from the end of a stick
About the Word:
Although it originally involved an unsavory pastime in which sticks were used to hurl frogs into the air, this word has had other meanings as well. For example, one 19th century report refers to a particular horse's insistence on "spanghewing" its riders.
(Spang, by the way, is a verb in its own right. It's mostly used in Scotland and means "throw" or "jump.")