The term 'severely simple' can be described by two crossword solutions: AUSTERE (7 letters) and STARK (5 letters). AUSTERE means having a stern or strict bearing, and is often used to describe a person's demeanor or a place's atmosphere. STARK, on the other hand, means bare or unadorned, and is often used to describe a place's appearance. Together, these two words can be used to describe something that is severely simple in both its look and feel.