task·mas·ter 
(tăskmăs′tər)
(tăskmăs′tər)n.
A person who regularly imposes difficult or demanding tasks.
- counterintuition
- counterintuitive
- counterintuitively
- counterirritant
- counterirritation
- counterman
- countermand
- countermarch
- countermeasure
- countermine
- countermove
- countermovement
- counteroffensive
- counteroffer
- counterpane
- counterpart
- counterparty
- counterperson
- counterplan
- counterplay
- counterplot
- counterpoint
- counterpoise
- counterpose
- counterproductive