Lewis Short
ob-murmŭro, āvi, ātum, 1
* V. n., to murmur against, at, or to (poet. and in post-Aug. prose); constr. with dat. or acc.: precibusque meis obmurmurat ipse,Ov. H. 18, 47: itidem obmurmurasse: Τί γάρ μοι, etc., Suet. Oth. 7: Pharisaei, quod, etc., Ambros. Cain et Abel, 2, 4, 16: obmurmurando dicere (with object-clause), Front. 4, 6, 2.
Charlton T. Lewis, Charles Short, A Latin Dictionary