1. Given to stopping and refusing to go on: a balky horse; a balky client.
2. Difficult to operate or start: a balky switch; a balky engine. -- American Heritage Dictionary
given to balking; stubborn; obstinate: a balky mule -- Dictionary.com
Came across this in this Los Angeles Times photo caption about the Mars rover: "A balky wheel on Spirit, one of two rovers that landed on Mars in 2004, scraped the soil to uncover silica deposits that could be evidence of ancient conditions hospitable to life."
Which leaves me to wonder: Could an ancient civilization on Mars have been any less familiar with the word "balky" thank I was?