An initialism of "in my not at all humble opinion," used primarily in online communications to express opinions one feels no modesty about. Used in humorous opposition to "IMHO" ("in my humble opinion"). I've been a member of this message board since day one, and it has really gone downhill in recent years (IMNAAHO). The premise is interesting, but IMNAAHO the writing and acting is just laughable.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.