| sing soprano | | | |
| sinking ship | | | |
| sit back | | | |
| sit on | | | |
| sit on one's hands | | | |
| sit through | | | |
| sitting pretty | | | |
| six of one, half a dozen of the other | | | |
| six ways to Sunday | | | |
| skate one's lane | | | |
| skeleton at the feast | | | |
| ski-jump nose | | | |
| skin trade | | | |
| skirt chaser | | | |
| skyrocketed | | | |
| slap leather | | | |
| sleep | | | |
| sleep in | | | |
| sleep in heavenly peace | | | |
| sleep together | | | |
| sleeves from one's vest | | | |
| sling along | | | |
| sling to | | | |
| slip of the tongue | | | |
| slip the cable | | | |
| slit someone's throat | | | |
| slow-burn | | | |
| slow off the mark | | | |
| slow-walk | | | |
| small change | | | |
| small print | | | |
| smart as a whip | | | |
| smash someone's face in | | | |
| smell a rat | | | |
| smell like a tart's handbag | | | |
| smell one's own farts | | | |
| smile from ear to ear | | | |
| smoke out | | | |
| smooth down | | | |
| snake eyes | | | |
| snap back | | | |
| snap out of | | | |
| snatch the pebble | | | |
| sneck posset | | | |
| snipe hunt | | | |
| snowball effect | | | |
| snow job | | | |
| snuggle bunny | | | |
| so be it | | | |
| social lubricant | | | |
| so far | | | |
| soften the blow | | | |
| soft Mick | | | |
| soft spot | | | |
| some old | | | |
| someone's jaw dropped | | | |
| something is rotten in the state of Denmark | | | |
| somewhere over the rainbow | | | |
| songbird | | | |
| sore-thumbish | | | |
| so true, bestie | | | |
| soup-to-nuts | | | |
| sour tooth | | | |
| space out | | | |
| spanner in the works | | | |
| spare tire | | | |
| speak for oneself | | | |
| speak of the devil and he shall appear | | | |
| speak to | | | |
| spearhead | | | |
| special relationship | | | |
| speech is silver, silence is golden | | | |
| sperm donor | | | |
| spiff up | | | |
| spill one's seed | | | |
| spin doctor | | | |
| spin someone's wheels | | | |
| spit in the wind | | | |
| spit out | | | |
| splash down | | | |
| split one's sides | | | |
| split up | | | |
| spoil someone rotten | | | |
| spot check | | | |
| spread one's wings | | | |
| spring for | | | |
| spruce up | | | |
| square on | | | |
| squash the beef | | | |
| stab in the dark | | | |
| stage business | | | |
| staircase wit | | | |
| stand and deliver | | | |
| stand corrected | | | |
| stand firm | | | |
| stand in one's own light | | | |
| stand on ceremony | | | |
| stand on one's own two feet | | | |
| stand pat | | | |
| stand to reason | | | |