The term 'AGAINST prefix' refers to a group of six words that all have the same prefix. The words are CONTRA (6 letters), ANTI (4 letters), ECO (3 letters), AERO (4 letters), NEO (3 letters), and CATA (4 letters). CONTRA means 'opposite or AGAINST, ' ANTI means 'opposing or hostile, ' ECO means 'environmentally friendly, ' AERO means 'relating to air or atmosphere, ' NEO means 'new or recent, ' and CATA means 'downward or opposite.' All of these words share the prefix 'AGAINST, ' which indicates opposition or hostility.