1) Arduous 2) Cumbersome 3) Heavy 4) Onerous 5) Taxing 6) Tiring 7) Unwieldy 1) Arduous 2) Difficult 3) Distressing 4) Exclusively Anglo word 5) Exclusively Saxon word 6) Hard to bear 7) Heavy 8) Not easily borne 9) Onerous 10) Oppressive 11) Oppressively heavy 12) Taxing 13) Tedious 14) Time-consuming 15) Tiring 16) Troublesome 17) Wearing 18) Word of purely Anglo origin 19) Word with Anglo-Saxon origins 
• (a.) Grievous to be borne; causing uneasiness or fatigue; oppressive.
Bur'den·some adjective Grievous to be borne; causing uneasiness or fatigue; oppressive. « The debt immense of endless gratitude So burdensome . Milton. » Syn. -- Heavy; weighty; cumbersome; onerous; grievous; oppressive; troublesome. -- Bur'den*some*ly , 
[adj] - not easily borne
onerous adjective not easily borne; wearing; `the burdensome task of preparing the income tax return`; `my duties weren`t onerous; I only had to greet the guests`; `a taxing schedule`
oppressively heavy; onerous. · distressing; troublesome. · having a full hull form, as a merchant vessel built for capacity rather than speed.