| stifle | muffle |
| stimulus | energizer |
| stockpile | saving |
| stoic | a person who has great self-control and who endures pain, discomfort or misfortune without complaning or showing signs of feeling it |
| stolid | emotionless |
| stout | bold |
| strapping | well-built |
| stratify | grade |
| strident | loud and brash |
| stringent | tough |
| studied | calculated |
| stupefy | overwhelm |
| stymie | deadlock |
| suave | charming, polite, elegant |
| subdue | control |
| subdued | not very loud |
| subjective | nonobjective |
| sublime | glorious |
| submissive | comfortable |
| subsequent | following |
| subterfuge | trickery |
| subvert | undermine |
| succinct | concise |
| succumb | to accept defeat |
| suffice | satisfy |
| suffrage | vote |
| suggestive | indicative |
| suitor | admirer |
| sullen | gloomy |
| sully | dirty |
| summit | zenith |
| sumptuous | splendid |
| supercilious | arrogant and disdainful |
| superficial | shallow |
| superfluous | excessive |
| suppress | crush |
| surfeit | abundance |
| surly | sullen |
| surmise | suppose |
| surreptitious | clandestine |
| susceptible | vulnerable |
| sustenance | support |
| sweeping | extensive |
| sycophant | flatterer |
| symbiotic | cooperative |
| symmetry | proportion |
| taboo | ban |
| tacit | silent |
| taciturn | saying very little |
| taciturnity | state of little speech |
| tandem | a relationship of two people or things that depends on cooperation |
| tangential | at a tangent to something |
| tantalizing | alluring |
| tantamount | equivalent |
| tattered | ragged |
| taunt | jeer |
| taut | tense |