Two words
May be 2 words combined (de+planus) If not obvious, probably incorrect
de PREP ABL
de PREP ABL [XXXAO]
down/away from, from, off; about, of, concerning; according to; with regard to;
plan.us ADJ 1 1 NOM S M POS
planus, plana -um, planior -or -us, planissimus -a -um ADJ [XXXBX]
level, flat;
*