Requite
To return/Repay
Restive
Restless, uneasy
Reticent
Silent; Reserved
Rhetoric
Effective writing/speaking
Ribald
Humorous in vulgar way
Rococo
Very highly ornamented
Rustic
Rural
Sacrosanct
Very sacred
Sagacious
Wise
Salient
Prominent
Salubrious
Healthful
Sanguine
Cheerfully optimistic
Sardonic
Cynical
Satiate
To satisfy
Scintilla
Trace amount
Sedition
Behavior promoting rebellion/civil disorder
Sentient
Aware
Seraphic
Sweet; angelic
Sinecure
Well paying job with little to no work
Slake
To calm down or moderate
Sobriquet
nickname
Solecism
Grammatical mistake
Soporific
Causing sleep or lethargy
Spartan
Highly self-disciplined