Here is our list of American idioms that start with "R":

(To) rack one's brain:
To try very hard to think of something. Example: "I racked my brain, but I couldn't remember his name."

Rain or shine:
No matter what the weather is like. Example: "The game will be played tomorrow, rain or shine."

(To) raise (some) eyebrows:
To shock. Example: "The art show raised some eyebrows due to its explicit content."

Rake in: To make a lot of money; Example: "He's really raking it in these days."

(To) read between the lines:
To try to understand what is meant by something that is not written/said clearly. Example: "I need to have things spelled out for me. I'm terrible at reading between the lines."

Red eye (n.): An overnight flight; Example: "I caught the red eye to Denver."

(A) redneck:
Generally refers to someone who has either bigoted or narrow-minded opinions. Often used in the context of people who live in small towns or in the country. Example: "Just because he's from rural Kentucky doesn't mean he's a redneck."

(A) regular guy:
A normal, average man (said in a fairly positive way). Example: "John? I don't know, I guess he's just a regular guy."

(To) rest one's case:
When people say "I rest my case", it usually means that they feel that they just proved that they are correct.

Ride (n.): Car. Example: "Nice ride!"

Ride shotgun (v.): To ride in the front passenger seat of a car. Example: "I wanna ride shotgun!"

Right off the bat:
Right away; immediately. Example: "I knew there was something wrong with him right off the bat."

(To) ring in the new year:
To celebrate the beginning of the New Year at midnight on December 31st. Example: "This year, we'll be ringing in the new year in Paris."

(To) ring a bell:
To remind someone of something. To vaguely recognize something. Examples: "P1: Have you every listened to Alex Chilton? P2: I'm not sure; the name rings a bell, though." ( = I think I've heard the name before.); "I'm sorry, that doesn't ring a bell." = I'm sorry I don't recognize/know that.

(A) rip-off or (To) rip-off:
A rip-off is something that costs more than it should. Example: "The popcorn prices at the movie theater are a rip-off."; To rip someone off means to steal from someone, or to cheat someone. Example: "The mechanic ripped me off."

(To) risk one's neck (to do something):
To risk (sometimes physical) harm to accomplish something. Example: "He's always been very mean to me. I don't plan to risk my neck to save his job."

Road rage (n.): The modern phenomenon of angry, aggressive driving, which sometimes leads to arguing, fighting, etc. between drivers.

(To) rob the cradle:
To go out with (or marry) someone who is much younger than you are. Example: "Victor's new wife is 25 years younger than him. Talk about robbing the cradle!"

Rock (v.): To be great. Example: "That rocks!" (That's really great!)

(To) rock the boat:
To disturb an otherwise stable situation. Example: "My grandmother wanted to express her disapproval, but she didn't because she didn't want to rock the boat."

Roll with it (v.): To go with the flow; To accept things as they come.

Rotten (adj):
Bad, nasty. Example: "I've done a lot of rotten things in the past."

(To) rub someone the wrong way:
To irritate someone. Example: "I'm not going out if your cousin is going. She really rubs me the wrong way."

(To) rub elbows with someone:
To associate with someone. Example: "When her singing career took off, Kathleen was able to rub elbows with the rich and famous."

Rule (v.): To be great/ the best. Example: "That band rules!"

(To) run a fever:
To have a fever. Example: "Jamie has been running a fever all day."

(To) run in the family:
To happen/ occur often in the family (through generations). Example: "P1: Frank is always so angry. P2: Yeah, his bad temper runs in the family."

Run (something) by (someone) (v.): To tell someone something, usually to get approval, etc. Example: "That's a good idea. I'll run it by my parents and see what they think."

(To give someone) the runaround/(To get) the runaround : To deceive someone, usually in the form of evasive excuses. Example: "I wanted to get some concrete answers, but they just gave me the runaround."