serious
overcomplicated
arduous
advanced
high
knotty
frob
situation
application
diligence
complexedness
unwieldiness
fancy
quantum mechanics
elaborate
perplexed
finagle
perplexity
incomplexity
difficult
uncomplexity
oversimple
mountain
endeavor
endeavour
Daedalian
strive
three-pipe problem
sophistication
hard
imponderable
higher
hard time
problematic
low
rough sledding
break a sweat
unsophisticated
opaque
unintelligible
crux
complicatedness
uncomplexed
uncomplicated
tough nut to crack
simplify
ambitious
complex
hard nut to crack
uneasy
baroque
complexness
effortfulness
overcomplicate
perplex
seek
essay
brainteaser
rubegoldbergian
mental gymnastics
complicate
assay
complexly
time-consuming
attempt
try
waltz
hard-fought
over one's head
trickily
sophisticate
solvate
mission impossible
Russian doll
complicated
tangled web
try as one may
poser
unresolvable
unsoluble
unsolvable
hard going
insolvable
exigency
way to run a railroad
undemanding
make a meal of
manual
convoluted
stumper
fucker
involute
struggle
involve
neat
work
task
serious
overcomplicated
arduous
advanced
high
knotty
fancy
elaborate
perplexed
difficult
oversimple
Daedalian
hard
imponderable
higher
problematic
low
unsophisticated
opaque
unintelligible
uncomplexed
uncomplicated
ambitious
complex
uneasy
baroque
rubegoldbergian
time-consuming
hard-fought
over one's head
complicated
unresolvable
unsoluble
unsolvable
insolvable
undemanding
manual
convoluted
involute
neat
complexly
trickily
situation
application
diligence
complexedness
unwieldiness
quantum mechanics
perplexity
incomplexity
uncomplexity
mountain
three-pipe problem
sophistication
hard time
rough sledding
crux
complicatedness
tough nut to crack
hard nut to crack
complexness
effortfulness
brainteaser
mental gymnastics
mission impossible
Russian doll
tangled web
poser
exigency
way to run a railroad
stumper
fucker
struggle
work
task
frob
finagle
elaborate
endeavor
endeavour
strive
break a sweat
simplify
overcomplicate
perplex
seek
essay
complicate
assay
attempt
try
waltz
sophisticate
solvate
make a meal of
involve
struggle
English words for 'requiring effort or concentration; complex and not easy to answer or solve'
As you may have noticed, above you will find words for "requiring effort or concentration; complex and not easy to answer or solve". Hover the mouse over the word you'd like to know more about to view its definition. Click 
to find a better fitting word. Finally, thanks to ChatGPT, the overall results have been greatly improved.
Recent Queries
a district
novelising
an illusion.
spade
foolishness.
pure love
linkage editor
cure-all
to enthrall.
merged company
shorthand symbol
to be better than
gin
a spree.
ambidexterity
day
Full of spirit
atomic layer epitaxy
symmetric key cryptography
dribbling
execute permission
tidal bore
a direction in music
You
cap
amortization
terminal care
out of date.
bankbook
to unmask
FYI
aqueduct
personal use
own.
stable.
to redo
good plan
definitely.
biennial plant
vomit.
sane
toxic substance
to harden
love scene
sarcastic
to crack
old age
to touch
major
keen