Definition of Overtax

Babylon English Dictionary
impose taxes that are too high; require too much, demand too much; overdo, overexert
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Overtax Definition from Language, Idioms & Slang Dictionaries & Glossaries
Webster's Revised Unabridged Dictionary (1913)
(v. t.)
To tax or to task too heavily.
  
Webster's Revised Unabridged Dictionary (1913), edited by Noah Porter. About
JM Welsh <=> English Dictionary
Gordrethu = v. to overtax
WordNet 2.0

Verb
1. tax excessively; "Don't overtax my constituents!"
(hypernym) tax