[1] : The Collaborative International Dictionary of English v.0.48

stepson \step"son`\, n. as. ste'opsunu.
   a son of one's husband or wife by a former marriage.
   1913 webster

[2] : WordNet (r) 2.0

stepson
     n : the son your spouse by a former marriage

[3] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

step-son. in latin privignus, is the son of one's wife, or of one's husband. 

Stepson >> S Words
Stepson, definition of term: Stepson
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