[anab.a.sis] n, pl -a.ses [Gk, inland march, fr. anabainein to go up or inland, fr. ana- + bainein to go--more at come] (ca. 1706) 1: a going or marching up: advance; esp: a military advance
2. [fr. the retreat of Greek mercenaries in Asia Minor described in the Anabasis of Xenophon]: a difficult and dangerous military retreat