spiny (adj.)

• abstruse
• acanthoid
• acanthous
• acicular
• acuate
• aculeate
• acuminate
• acute
• arduous
• barbed
• brutal
• complex
• critical
• cusped
• cuspidate
• delicate
• demanding
• difficult
• exacting
• formidable
• hairy
• hard
• hard-fought
• hispid
• horned
• horny
• intricate
• knotted
• knotty
• laborious
• mean
• nettlesome
• operose
• pointed
• prickly
• pronged
• rigorous
• rough
• rugged
• severe
• sharp-pointed
• spiked
• spiky
• spinous
• steep
• strenuous
• tapered
• tapering
• thorny
• ticklish
• tined
• toilsome
• toothed
• tough
• tricky
• uphill
• wicked