急 (Kanji for urgent)

Onyomi

KYUU

When some CUTE dudes get fishhooks stuck in their snouts while simultaneously having heart attacks, that's pretty urgent.

いそ*ぐ	to rush (usually in the present tense, like this : 急いで！（いそいで！）） ★★★★★

急に(きゅうに) xxx	suddenly ★★★★★ KUN ON
急行(きゅうこう)	express train ★★★☆☆ 急 (urgent) + 行 (go) = 急行 (express train)
緊急(きんきゅう) の　or に	urgent ★☆☆☆☆ 緊 (tense) + 急 (urgent) = 緊急 (urgent)