used as a wish that s.o. enjoy the meal he is eating or is about to eat
bon appitit!
enjoy your meal (your food etc)!enjoy!hearty appetite!
Костерок оказался у небольшого причала, пылал уже затухающим пламенем, освещая нескольких то ли геологов, то ли рыбаков и край большой лодки. «Здравствуйте, товарищи! - Подойдя ближе, Золотарёв присел позади них на корточки. - Приятного аппетита» (Максимов 1). The dying flames of the bonfire, which turned out to be at a little mooring-stage, lit up the faces of a group of men—geologists perhaps, or fishermen—and the edge of a large boat. "Good evening, comrades! Enjoy your food." Zolotarev went up and crouched beside them (1a).