Mark suggesting a 'c' should be pronounced an 's'

• Letter attachment?
• Mark under a letter c
• Mark in the intersection of 58-Across and 43-Down
• French diacritical mark
• Cousin of the tilde and umlaut
• Janet's fiancé in "The Rocky Horror Picture Show"

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
cedilla \ce*dil"la\ (s[-e]*d[i^]l"l[.a]), n. [Sp. cedilla, cf. F. c['e]dille; dim. of zeta, the Gr. name of the letter z, because this letter was formerly written after the c, to give it the sound of s.] A mark placed under the letter c [thus, [,c ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
c.1600, from Spanish cedilla , zedilla , literally "little z," from a Latin-like diminutive of Greek zeta "the letter 'z'." The mark (formerly also used in Spanish) was derived from that letter and indicates a "soft" sound in letters in positions where ...

Wiktionary Word definitions in Wiktionary
n. (context orthography English) In the spelling of Catalan, French, Portuguese and some other languages, a mark sometimes placed under the letter (term: c) to indicate that it is pronounced /s/ rather than /k/, as in French ''menaçant'' and Portuguese ...