Synonyms of upstream

1 Syllable

tough, stiff, trying

2 Syllables

heavy, painful, hard-won, strenuous, rigid, arduous, galling, problem, crucial, uphill

3 Syllables

ambitious, laborious, unyielding, demanding, challenging, backbreaker, effortful, toilsome, difficult, severe, gargantuan, titanic, onerous, immense, herculean, labored, exacting

4 Syllables

intricate, wearisome, difficile, operose, burdensome, irritating, bothersome, troublesome, formidable, problematic

5 Syllables

prohibitive