The term 'not as warm' can be described by four different words: icier (5 letters), stonier (7 letters), COLDER (6 letters), and COOLER (6 letters). Icier is an adjective meaning 'even COLDER than before, ' while stonier is an adjective meaning 'harder, more rigid, or less yielding.' COLDER is an adjective meaning 'having a lower temperature, ' and COOLER is an adjective meaning 'slightly cold.' All four words describe something that is not as warm as something else.