Hmmm ... 
 '''H'''ear'''M'''e'''M'''ake'''M'''eaning
Often used on this wiki ... and growing (456  on 20131115), up from the last check when it was 417, and before than 404 ) [http://www.c2.com/cgi/fullSearch?search=Hmmm]:
 
The word, or an absent of words, expressing deliberation and thought and an instant reaction to the foregoing expressions. The first word of a sentence, indicating a description, definition, a deflection or a diversion of topic is to follow. Then the expression of the writer ''off the cuff''. This is the first time I have used this, in reaction to a page NotDoing. Often the inclusion would be better if Hmmm stood alone, or was absent from what followed, or both were absent. It really seems to be saying LetMeThinkAboutThat!

Examples:

From AllModelsAreWrongSomeModelsAreUseful: (Note the triggering of the double Hmmm)

Hmmm. Sounds promising. I guess "All models are incomplete; some models are useful" works for me as well as the original, and apparently is getting a little closer to your point of view, too.

Hmmm, hmmm. Or maybe "All models are lacking; some models are useful". I kind of like the double meaning. But I think I see a pattern. Putting trigger words like "wrong" or "lie" or "bad" in cute little sayings is not always helpful.

From BadStuffWeLearnInSchool:

Hmmm... I would define a "full education", at least for the 19th century, as being the "very model of a modern Major General". :) A person with a full education would be fully literate, fully numerate (including trigonometry, geometry, and calculus), know geography, have a solid grounding in logical reasoning and history (both classical and modern), and have a reasonable grasp of the law. This would be the solid grounding required for further specialization.

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Hmmm. So "pop music" can't include "great songs"? I'd beg to differ. In Mozart's day, his music was very popular, no? Was Shakespeare specifically trying to create great works, or trying to pack the seats at the Globe? I would say that much of what we now call "great works" started out as the "pop culture" of its day. And, someday, that portion of our "pop culture" that stands the test of time will become "great works" for our descendants. -- MikeSmith

Hmmm. Mozart's music was popular (and known) probably only to the upper 5% or so of society. One of the great changes of the 20th century was the availability of "pop culture" to almost everybody, thanks to radio, records, and later TV and CDs. I don't think there was such a thing as "pop culture" in the 18th century. -- JohnWebber

I'm sure there were wandering musicians in the 18th century. There were certainly a number of shared myths and stories. Pop culture existed; it was just of a different form. -- BrentNewhall

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Seeing "hmmm", "um", "uh", "er", "eh?' written in prose is one of my personal PetPeeves. Such gestures are certainly useful in spoken converstation, but they are just noise in written communications. If you want to express the fact that you are unsure about something, then state that you are unsure. If you want to be in a chat room, go to a chat room. If you need to pause to think about something before writing, then ''don't write''. Please don't make me read your illiterate grunts and groans here in wiki. -- KrisJohnson

Mine too, That's why this page was started. It was my way of calling attention and encouraging an abandonment of such usage. (Which see -> NotDoing) -- DonaldNoyes