Added in 1.5

/devoice <nick> [nickN...]

Demotes nick from voice on current channel. (mode #channel -v Nick)

Parameters
<nick> - The nick to demote.
[nickN...] - Additional nicks to demote.

Example

;Demote 3 users.
/devoice Nick1 Nick2 Nick3

;Demote 1 user.
/devoice Nick1