requiring much effort, strength, skill or ability

hard on someone; hard to do

hard-working; showing care and effort

persevering, hard-working

an apparatus for grinding

hardworking

willing to work long and hard

hardworking

needing, showing, great effort

hard, difficult

slow and troublesome; not easy or natural

difficult to understand, unclear

using or needing great effort

difficult; requiring hard work

(moving) in the opposite direction to the stream or current

hard on someone; hard to do