menacing

(verb) pose a threat to; present a danger to. Synonyms: endanger, jeopardize, jeopardise, menace, threaten, imperil, peril. Example: "The pollution is endangering the crops."

(verb) express a threat either by an utterance or a gesture. Synonyms: menace. Example: "He menaced the bank manager with a stick."

(verb) act in a threatening manner. Synonyms: menace. Example: "A menacing person."

(adj) threatening or foreshadowing evil or tragic developments. Synonyms: baleful, forbidding, minacious, minatory, ominous, sinister, threatening. Examples: "A baleful look." "Forbidding thunderclouds." "His tone became menacing." "Ominous rumblings of discontent." "Sinister storm clouds." "A sinister smile." "His threatening behavior." "Ugly black clouds." "The situation became ugly."