fogsignal(n = noun.communication) foghorn - a loud low warning signal that can be heard by fogbound ships;
is a kind of alarm, alarum, alert, warning signal

N  alarm, alarum, larum, alarm bell, tocsin, alerts, beat of drum, sound of trumpet, note of alarm, hue and cry, fire cross, signal of distress, blue lights, war-cry, war- whoop, warning, fogsignal, foghorn, yellow flag, danger signal, red light, red flag, fire bell, police whistle, false alarm, cry of wolf, bug-bear, bugaboo, alarming, Int, sauve qui peut!, every man for himself!, qui vive?.