Lower is a synonym of Frown. Frown is the opposite of Smile. Smile is related to Say. Say is related to Speech. 
Bill is related to Bullet. Bullet is related to War. War is related to Aggressive. Aggressive is similar to Hostile. 
Lower <--Synonym--> Frown <--Antonym--> Smile <--RelatedTo--> Say <--RelatedTo--> Speech 
Bill <--RelatedTo--> Bullet <--RelatedTo--> War <--RelatedTo--> Aggressive <--SimilarTo--> Hostile 