R is for River Montag floated through the River to hide from the police helicopters. He put fakers clothes on to hide his scent from the mechanical hound also chasing after him.
S is for scent Montag has to find a way to mask his scent to avoid the hound. He has Faber burn things he's touched and asks for his oldest dirtiest clothes. When he leaves Faber will turn on his sprinklers.
T is for trace The mechanical hound and police are chasing after Montag. He's smart enough to cover up his tracks and leave behind no trace for them to find him.
U is for unliked Beatty was unliked by Guy so much he ended up burning Beatty to his death in front of Montag's house. After they burned Montag's house.
X is for xenogenous It means from and outside cause. The war happened because of an outside issue between countries that isn't explained why the war was declared in the book.