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5.
The repetition of meaning in the same sentence, using different words. Usually decreases clarity of speech/writing.
Example of a sentence using Tautology:
He struggled to lift the heavy weights, he had trouble raising them.
by Chaye June 24, 2009
 
1.
saying the same thing twice over in different words
Some people think this is an example of tautology:

It would be easy to find a blind man in a nudist colony because it wouldn't be hard.
by yorrick hunt January 22, 2008
 
2.
True by definition, literally "saying the same". Pointlessly obvious. Additional words that add no meaning.
"Either we'll get in trouble, or we won't" is a logical tautology. By including all possibilities the statement must inherently be true.

In "PIN number" the word "number" is a tautology because a PIN is always a number. (At least that's what the N originally stood for — if the term PIN evolved to include letters someday then PIN number would no longer be a tautology.)

In "morning sunrise" the tautology is "morning" because sunrises are a subset of mornings; removing the first word removes no meaning. (The addition of "morning" may be aesthetically more pleasing, in a poem for example, but it remains a logical tautology.)
by Bob Stein September 10, 2008
 
3.
Tautology (n): that which is tautologous, a tautology.
Jack built a brick house out of bricks.
The filing cabinet had inertia, it wouldn't budge.
Go sit in the corner where the walls and floor meet, boy!
The tautologous tautology
by Homfrog March 10, 2010
 
4.
Using different words to say the same thing, or a series of self-reinforcing statements that cannot be disproved because they depend on the assumption that they are already correct
ME: Dudes such a wanker he’s dead-to-me… like piss-on-his-grave dead-to-me…
FRIEND: Thats a hell-of-a tautology if i have ever heard one.
by BNENJK September 25, 2012
 
6.
Unnecessary repetition of a word.
HIV virus
PIN number
by Verity November 10, 2004
 
7.
A tautology is a reiteration of a term using one or more different successive synonyms.
Examples of tautology:

It was a wet rainy day with lots of precipitation.
She is a female woman of the opposite sex, John.
We could see some dilapidated ruins.
by Fearman December 03, 2007