Both Uses of

wanton

in

The Merchant of Venice

Look on beauty And you shall see 'tis purchas'd by the weight: Which therein works a miracle in nature, Making them lightest that wear most of it: So are those crisped snaky golden locks Which make such wanton gambols with the wind, Upon supposed fairness, often known To be the dowry of a second head, The skull that bred them, in the sepulchre.†
Scene 3.2 *

The reason is, your spirits are attentive; For do but note a wild and wanton herd, Or race of youthful and unhandled colts, Fetching mad bounds, bellowing and neighing loud, Which is the hot condition of their blood; If they but hear perchance a trumpet sound, Or any air of music touch their ears, You shall perceive them make a mutual stand, Their savage eyes turn'd to a modest gaze By the sweet power of music: therefore the poet Did feign that Orpheus drew trees, stones, and floods; Since nought so stockish, hard, and full of rage, But music for the time doth change his nature.†
Scene 5.1

Definitions:

(1) (wanton)
of something considered bad: excessive, thoughtless indulgence -- such as waste, cruelty, violence, and (especially in the past) sexual promiscuity
(2) (meaning too rare to warrant focus)
In classic literature, wanton can also describe people who are playful or plants that are growing profusely.