Definition of Dumb

dumb (dum)
dumb·er, dumb·est adj.
dumbly adv.
dumbness n.

1. a) Lacking the power of speech; b) Often Offensive Incapable of using speech; mute.

2. Temporarily speechless, as with shock or fear: I was dumb with disbelief.

3. Unwilling to speak; taciturn.

4. Not expressed or articulated in sounds or words: dumb resentment.

5. Nautical Not self-propelling.

6. Conspicuously unintelligent; stupid: dumb officials; a dumb decision.

In ordinary spoken English, a sentence such as He is dumb will be interpreted to mean "He is stupid" rather than "He lacks the power of speech." "Lacking the power of speech" is, however, the original sense of the word, but it has been eclipsed by the meaning "stupid." For this change in meaning, it appears that the Germans are responsible. German has a similar and related word dumm that means "stupid," and over time, as a result of the waves of German immigrants to the United States, it has come to influence the meaning of English dumb. This is one of dozens of marks left by German on American English. Some words, like kindergarten, dachshund, and schnapps still have a German feel or are associated to some extent with Germany, but others, like bum, cookbook, fresh (in the meaning "impertinent"), rifle, and noodle have become so thoroughly Americanized their German origins may surprise some.
The above exerpt is from The American Heritage® Dictionary of the English Language, Fourth Edition copyright ©2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

I always felt it was important to distinguish what I meant by "Dummies" especially while putting it in the same sentence as "Positivity".

I mean someone who doesn't speak up when they should; someone who doesn't care about their fellow man; someone who is close minded. Positivity is spread by speaking up about injustices; making a change for the better in yourself, your family, and your community; being open to other's beliefs and ideas...You get the idea.