a preteen who acts like their in love, even though they have no idea what love is. A ninnywillow can also be a girl, who is in love with a guy but will not admit it.
Sidney is such a ninnywillow. She's dated Rob for two days, and says that she's in love with him.

Jess is such a ninnyillow. She won't admit that she's in love with Tim even though it's so obvious.
by ConDOh April 24, 2009
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