What's your preferred shorthand for "Climbing Partner"? I'm looking for better cardinality than "Partner".

Back to the original question...

If you're climbing trad with someone, they are your PRO BRO.

Comrade!

Calebwrote:

Comrade!

love it. "Comrade" is one a military climbing buddy consistently uses as his go-to for "My friend!" 

It's funny to me that it primarily has strong cold war soviet overtones in my mind, but apparently it comes from the Spanish "camarada", simply meaning roommate, before the term became militarized.

Which reminds me of another of my favorites - compadre - which literally translates to "friend who helps look out for the younger generation."

I’ve got tree climbing buddy who calls everyone “compadre”.  It works for him in a surfer/cowboy kinda way.

“Friend” works pretty well too, though it can sound disingenuous, closeted or euphemistic.

Bonhomme another fun option that just came to mind.

Especially if they tend to grab a lot of draws and aid the harder moves   

For those of you not into the whole brevity thing, might I suggest:

 my cragging confederate

 my similarly syndicated simian

 my abseil abettor

 my co-conspirator

For those of you with an affinity for acronyms: the Person With Whom I Climb

It would be nominally pronounced "pwick" or "pwike", depending on whether it's used in the first person, or second person...

 as in: "So, your PWWYC is a no-show?"  "Yeah, my PWWIC ain't here.  Go figure."