Literary or historical term for a fortification. Often appears in compounds like 塁壁 (rampart) or 孤塁 (isolated fortress).
They captured the enemy fortress.
The batter advanced to second base.
The runner advanced to second base.
He succeeded in stealing a base.
The soldiers built a rampart on the riverbank.
The runner is standing on first base.
They kept defending the isolated stronghold with a small number of soldiers.
塁 (base; fortress) and 累 (accumulation; involvement) share the same reading るい but have completely unrelated meanings.
Standard kanji spelling; used in both baseball and fortress senses.
The kanji 塁 originally depicted piled earth and is associated with ramparts and fortifications. The baseball sense is a semantic extension from the idea of a 'base' as a defended position.
base umpire
third baseman
runner left on base; leaving runners on base · remnant fort; remaining fortification
earthen wall; earthwork; embankment
horst
fortress; stronghold
stronghold; fortified position
fort; fortress; stronghold
on base · on a fort; on a rampart
rampart; fortification wall
softball
isolated stronghold; isolated fort
returning to base; tagging up