inadequate
not good enough
incurable
not able to be healed of an illness, untreatable
inactive
not involving much physical activity
incomplete
not having all the necessary parts, not finished
insecure
not confident or assured, uncertain or anxious; OR easily broken (unprotected)
invisible
unable to be seen
inelegant
not showing grace or refinement, clumsy, ungraceful
inflexible
not willing to change or compromise (stubborn); OR not able to bend (rigid)
inability
the state of being not capable of doing something
indefinite
lasting for an unknown length of time
insane
not in a normal state of mind, crazy
independent
not relying on another person to take care of your needs
invalid
not founded in truth or logic
involuntary
done without your control (like a sneeze)
insignificant
not important
inexpensive
does not cost a lot