Sentence:  Plants rais'd with tenderness are seldom strong, / Man's <WSD>coltish</WSD> disposition asks the thong ["i.e." whip], / And without discipline the fav'rite child, / Like a neglected forrester runs wild. 
Meaning of the word marked with <WSD> tags:  Lively, playful and undisciplined (often in a manner judged to be immature).<ref>B.(nbsp)E., "A New Dictionary of the Canting Crew," London: W. Hawes "et al.," 1699: “Coltish, said when an old Fellow is frolicksom or wanton; or he has a Colt's Tooth.”[http://name.umdl.umich.edu/A39127.0001.001]</ref>