To make unfit; to render unsuitable, spoil, disqualify.
"The sudden downpour rendered the muddy field unfit for the tractor's heavy machinery."
not in good physical or mental condition; out of condition
"fat and very unfit"
"certified as unfit for army service"
"drunk and unfit for service"
Not fit; not having the correct requirements.
"The new software update proved unfit for our older servers, causing them to crash immediately upon startup."