What is the verb for incomprehensible?

There isn't a single verb that perfectly captures the meaning of "incomprehensible." However, depending on the context, you could use several verbs to convey a similar idea:

For something that is difficult to understand:

* Confuse: "The instructions confused me."

* Baffle: "The complex math problem baffled her."

* Mystify: "The ancient writings mystified scholars."

* Puzzle: "The strange noises puzzled the residents."

* Bewilder: "The sudden change in plans bewildered her."

For something that is completely beyond understanding:

* Defy: "The language defied translation."

* Transcend: "The artist's work transcended comprehension."

* Elude: "The meaning of the poem eluded me."

* Escape: "The logic of their argument escaped me."

For something that is unintelligible:

* Garble: "The phone call was garbled."

* Mumble: "He mumbled something incomprehensible."

* Slur: "His speech was slurred and unintelligible."

* Distort: "The radio signal distorted the message."

The best verb to use will depend on the specific situation and the nuance you want to convey.