This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

v. To task too heavily, to give someone or something to many tasks; overburden

v. To task too heavily.

To impose too heavy a task or duty upon: as, to overtask a pupil; to overtask the memory.

"Operation comes to overtask us, either through the admixture of useless matters, or through the multiplicity of instruments, or through the bulk of the material and of the bodies that may happen to be required for any particular work."

overtasked