to be involved in an activity that could be dangerous.

We're playing with fire if we continue with genetic modification of our food. (usually in continuous tenses)

• be dead in the water
• be dead meat
• be dead on feet
• be dead on your feet
• be dead to the world
• be department
• be done in
• be done like a dinner
• be done like a dog's dinner
• be done to a turn
• be done to death
• be down in the dumps
• be down in the mouth
• be down on like a ton of bricks
• be down on luck
• be down on someone like a ton of bricks
• be down on uppers
• be down on your luck
• be down on your uppers
• be dressed to kill
• be dressed up to the nines
• bedroom eyes
• be dropping like flies
• be duck soup
• be duty bound