Use 'knotty' to describe problems that are not only complex but also messy or tangled in nature. Trying to plan the event schedule turned into a knotty task due to conflicting timings.
Pro Tip 2/3
Intellectual Challenge
'Knotty' is often used for intellectual challenges that require a lot of thought to unravel. The philosopher's knotty argument took me weeks to fully understand.
Pro Tip 3/3
Debate and Discussion
In discussions, 'knotty' describes issues that are hard to agree upon or resolve. The committee faced a knotty issue that sparked hours of debate.