Onerous

a.

1.

Burdensome; oppressive. Onerous cause (Scots Law) a good and legal consideration; - opposed to gratuitous.

Adj.

1.

onerous - 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" Synonyms: burdensome, taxing

Herculean, annoying, arduously, backbreaking, besetting, bothersome, burdensomely, crushing, cumbersome, cumbrous, demanding, difficultly, effortful, encumbering, exacting, exhausting, exigent, forced, grievous, grinding, grueling, hampering, hard-earned, hard-fought, hardly, harsh, heavy, heavy-handed, hefty, impedimental, impeding, impeditive, incumbent, irksome, killing, labored, laborious, laboriously, lumpish, massive, onerously, operose, oppressive, overburdensome, painful, plaguey, ponderous, punishing, strained, strenuous, superincumbent, taxing, toilsome, toilsomely, tough, troublesome, trying, tyrannous, unruly, unwieldy, uphill, vexatious, wearing, wearisome, wearying, weighty