hard
/ˈhärd/
adjective
not easily penetrated : not easily yielding to pressure
having a bitter or acidic taste
hard surfaces
adverb
with great or utmost effort or energy : strenuously
in a violent manner : fiercely
to the full extent —usually used in nautical directions
were hard at work
hit the ball hard
adjective
not to be modified or evaded : strict
a hard-and-fast rule