a large circular strip of rigid material, used:
for holding together the staves of a barrel
for bowling along the ground or exercising with
a hula hoop
formerly, for expanding a woman's skirt
typically paper-covered, for animals to jump through in a circus
a circular figure or object
‘What's the matter?’ ‘About a hoop of gold, a paltry ring that she did give me.’ — Shakespeare
an arch through which balls must be hit in croquet
a horizontal band of contrasting colour round a cap or sports shirt
Aus, informal a jockey (from the band round his shirt)
be put/go through the hoops
to undergo a demanding series of tests
[Old English hōp]