Interest Rate Ceiling
  
See: Interest Rate Collar.
The ceiliing is the highest rate, in a given debt covenant, that the interest rate can attain, usually as defined to exist within a given period.
Like..."the interest on this adjustable rate mortgage shall be the rolling arithmetic average of the last 3 months' LIBOR rates plus 100 basis points, but shall not exceed 7% for the lifetime of the mortgage." That 7% figure is the ceiling.