hasta

Hasta, hastae is feminine, first declension, and declines with no surprises at all. It is the thrusting spear rather than the pilum, the heavy javelin a legionary threw and then abandoned, so a text that distinguishes the two is telling you about tactics.

The word does duty well outside the battlefield. A spear planted in the ground marked a public auction, so "sub hasta vendere" is to sell at auction and "hasta" alone can mean the sale itself; property confiscated from the proscribed went that way. The hasta pura, a spear with no iron head, was a military decoration. Italian asta keeps both the spear and the auction.