underdo verb. [ʌndǝ'du:] Infl. as DO verb; pa. t. usu. -did [-'dɪd], pa. pple usu. -done [-'dʌn]. E17.
[from UNDER- + DO verb.]
1. verb intrans. Do less than is requisite or necessary. Now rare. E17.

2. verb trans. Do (a thing) inadequately or incompletely; esp. cook (food) insufficiently or lightly (chiefly as UNDERDONE adjective). E18.

[TahlilGaran] English Dictionary ▲