Helpless or easy?

Hi.
I wonder if sitting ducks are helpless, defenseless, or ease targets or victims? There are different dictionary difinitions:

sitting duck

n. Informal
An easy target or victim.

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.

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sit'ting duck'
n.

a helpless or easy target or victim.

[1940–45]

Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.


Thanks in advance