Grow out of control is a phrase that is used to describe a situation in which something increases rapidly and uncontrollably. The two crossword solutions for this phrase are MUSHROOM (8 letters) and SNOWBALL (8 letters). MUSHROOM is a type of fungus that grows quickly and can spread rapidly if not managed properly. SNOWBALL is a metaphor for something that increases quickly and exponentially, like a SNOWBALL rolling down a hill and growing larger as it goes.