sannisīdati : [saṃ + ni + sad + a] settles; subsides; becomes quiet.

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]

Sannisīdati [saŋ+nisīdati] 1. (lit.) to sink down, to settle Miln 35. -- 2. (fig.) to subside, to become quiet M i.121; S iv.196; A ii.157. -- Caus. sannisādeti to make quiet, to calm M i.116; A ii.94. -- Caus. II. sannisīdāpeti to cause to halt J iv.258. -- pp. sannisinna.

Pali-English Dictionary, TW Rhys Davids, William Stede,