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1.
Type One: A Granola MILF, or a MILF that enjoys the outdoors and eats particularly healthy.

Type Two: A lactating MILF, who has recently given birth.
Dude, did you check out that chick on the hiking trail, she was a total Soy MILF.

Dude, did you see that babe at the day care center, she was a complete Soy MILF.
by The original Soy MILF January 31, 2010
 
2.
A hippie, burner or vegan mother you would like to share intimate relations with.
I love going to Whole Foods to check out all the soymilfs.
by YouturnTexas September 20, 2011