тежок

Etymology
, from.

Adjective

 * 1) heavy, weighty, ponderous, elephantine
 * 2) hard, difficult, arduous, burdensome, cumbersome, cumbrous, onerous, severe, tough, grueling, painful, trying
 * 3) serious, grave, important, grievous
 * 4) (predicatively with zero copula in the neuter singular) improbable