| sleeper | n. | railroad tie; horizontal load-distributing wooden beam | British | |
| slewfoot | n. | detective, policeman; clumsy person | slang | |
| slipe | v. | to peel, to strip away an outer covering | ||
| sloe | n. | astringent fruit of the blackthorn | ||
| slope | v. | to go surreptitiously | British | |
| sloper | n. | basic tailoring pattern without allowance for different seams or styles, usually made for a specific individual | ||
| Sloppy Joe | n. | loose-fitting comfortable jumper or sweatshirt | ||
| slough | n. | a state of profound despair [pronounced “sloo”] | ||
| slue | v. | to turn about an object’s axis; to swing around | ||
| sluff | v. | to shed; to ignore, to discard; to goldbrick | ||
| slungshot | n. | weight attached to small cord used to cast lines from one place to another; similar device with shorter rope used as a weapon similar to a blackjack | nautical | |
| slut’s wool | n. | dust and debris that gathers beneath furniture (in supposed reference to slatternly housekeeping habits) | idiom | |
| slype | n. | covered passageway, esp. from chapter house to a cathedral’s transept | architecture | |
| small-clothes | n. | underwear | archaic | |
| smalt | n. | powdered glass admixed with cobalt oxide, used to add color to glass products | ||
| smaragdine | adj. | of or relating to emeralds; emerald green | ||
| smarm | v. | to smooth down with ointment or grease; to fawn over | ||
| smellfungus | n. | one who finds faults, grumbler | archaic | |
| smoker | n. | casual get-together for men at which cigars or other tobacco products are smoked | informal | |
| smudger | n. | photographer, photojournalist | slang | |
| smut | n. | soot particle | ||
| smutch | v. | to smudge or soil; to stain, to sully | ||
| snaffle | n. | large ringed horse bit | ||
| snaffle | v. | to purloin, to swipe | British | |
| sneap | v. | to pinch; to repress, to chide | ||
| sneck | n. | door or window latch | Scots | |
| snib | v. | to latch | Scots | |
| snollygoster | n. | shrewd unscrupulous person | ||
| snooks | n. | rude gesture in which one puts the thumb on the nose and extends the fingers | ||
| snooter | n. | snooty person, snob | informal | |
| snorter | n. | rip-roarer, remarkable thing; one who snorts | slang | |
| snug | v. | to lash down or stow away, as in preparation for a storm | nautical | |
| snuggery | n. | cozy or comfortable room, esp. of small size | British | |
| sobriquet | n. | nickname | ||
| socage | n. | tenure of land by rent or service not including military service | ||
| sockdolager | n. | knockout blow, decisive argument or reply; unusually heavy or large thing | ||
| sodality | n. | companionship, fellowship; an association; society for Catholic laypeople | ||
| soffit | n. | under surface of architectural feature, such as a lintel, architrave, vault, or arch | ||
| sogering | v. | goldbricking, shirking hard work | obsolete | |
| soigné | adj. | well-groomed, fashionably made up | ||
| soilure | n. | act of soiling; staining, dirtiness | ||
| solecism | n. | grammatical error; breach of good manners; any inconsistency or error | ||
| solfeggio | n. | do-re-mi system of learning notes of the scale | ||
| solideme | n. | undivided unhyphenated compound word | ||
| soothmoother | n. | outsider | Scots | |
| sorb | n. | fruit-bearing deciduous tree of the old world, the service tree; the fruit of this tree | ||
| sorites | n. | series of propositions or syllogisms where each conclusion becomes the subject of the next | rhetoric | |
| sorn | v. | to sponge off, to mooch | Scots | |
| sorted | adj. | completed, organized, arranged | ||
| sotadic | adj. | of erotic or pornographic material (after Sotades, the first known Greek erotic poet) |