supersessive - to take the place of, or cause to be supplanted

sperstition, supple, suppletory, suppliant, supply, supposition,, supremacy

surcingle
n.
5ME surcengle < MFr < OFr sur3, SUR31 + L cingulum, a belt: see CINGULUM6
1 a strap passed around a horse‘s body to bind on a saddle, blanket, pack, etc.
2 [Historical] the belt of a cassock

surmisable, surprising, surrealist, surrender,

surrogate
n.
5L surrogatus, pp. of surrogare, to elect in place of another, substitute < sub3 (see SUB3) + rogare, to ask: see ROGATION6
1 a deputy or substitute
>2 in some States, probate court, or a judge of this court
3 Psychiatry a substitute figure, esp. a person of some authority, who replaces a father or mother in one‘s
surveil, suspiciously, suspiration,

sussultatory = up and down wide amplitude movements, as in some earthquakes

swampy, swarming, swindler, switch, swizzle,

syagush - outside of the spelling bee site, this word was found only in a couple weirdo sites, and one porno site

sycophants
sycosis
n.
5ModL < Gr sykbsis < sykon, fig + 3bsis, 3OSIS6 a chronic disease of the hair follicles, esp. of the beard, caused by certain staphylococci and characterized by the formation of papules and pustules

syllabary, syllabic,

syllepsis
n.,
pl. 3lep4ses# 73scz#8 5L < Gr syllcpsis, a putting together < syllambanein: see SYLLABLE6 a grammatical construction in which a single word is used in a syntactical relationship with two or more words in the same sentence, though it can agree with only one of them in gender, number, or case (Ex.: either they or I am wrong)
syl[lep4tic
adj.
symbiotically

symblepharon - I would have thought the word meant “adhesion of the eyelids”. Here is a picture of it, but no
definition - http://www.mrcophth.com/oculoplasticgallery/oculoplastic2/symblepharon.html

sympatry, symphonette, symptomatic, symptoms, synanthus = some goofy botanical epithet .
synchnocarpous = another botanical epithet