Technically, the word anabasis is a noun, and means (according to the AHD):

1. An advance; an expedition.
2. A large-scale military advance, specifically the Greek mercenary expedition across Asia Minor in 401 B.C. led by Cyrus the Younger of Persia, as described by Xenophon (who was there) and later wrote a book about it, and the the "ten thousand" who followed Cyrus. It was unsuccessful, and the Greeks, led by Xenophon, retreated to the Black Sea.

Teddy Roosevelt's charge up San Juan hill, in terms of his initial strategy, would qualify as an anabasis. The word seems to have come into being via the works of the Greek philosopher and historian Xenophon, who used anabasis to refer to spectacularly unsuccessful expedition by Greek mercenaries across Asian Minor in 401 B.C. (including, by the way, Celtic mercenaries from Gaul) led by Cyrus the Younger of Persia. Xenephon used the word anabasis in his title.

Etymologically, anabasis is a word with a Greek pedigree, derived from the Greek verb anabainein, "to go up." It's related, etymologically, to the word anabaena, a variety of freshwater algae that sometimes occurs in drinking water and causes a bad taste and odor, that "goes up," so to speak, so that the odor is very noticeable. Anabainein may be traced back to the Proto Indo-European root * g^w?-, meaning "to go, come" which also gives us words like "become, come, welcome" in English, and related words in Latin and French derived from Latin venire, "to come."

Anabasis articulata is also a wildflower, a species of Chenopodiaceae found on the high desert slopes of Israel, the Samarian desert, the Judean desert and the floor of the Dead Sea valley, Northern Negev, Negev hills and Eilat, Aravah, in the Middle East. There's a picture of the flower above.

The plural of anabasis is anabases, and the adjective form is anabatic, a word typically used to describe the wind currents that flow up an extreme altitude mountainside.