From the second edition (1989):
[Back-formation f. prec. But cf. OF. sillabifier (15th c.).]
trans. ‘To form or divide into syllables’ (Webster, 1864). Also intr.
1926 [see syllabization]. 1954 F. G. Cassidy Robertson's Devel. Mod. Eng. (ed. 2) xii. 381 Though the American may syllabify more fully where the Englishman elides, he also slurs more. 1972 Language XLVIII. 357 If one assumes that ø is the alternative to syllabifying -s, then one can establish a graded gamut of markedness among the three alternants.