General use for something third in a sequence, often in compounds or titles such as albums, seasons, or versions.
彼らのサードアルバムは来月発売される。
Their third album will be released next month.
He plays third base for the team.
third base; third baseman
Baseball term. Depending on context, サード can mean the base, the fielding position, or the player at third base.
ランナーがサードに進んだ。
The runner advanced to third base.
彼は高校時代、サードを守っていた。
In high school, he played third base.
third gear
Vehicle or machinery use, especially when talking about gears in a manual transmission.
カーブの手前でサードに落とした。
I shifted down to third before the curve.
I shifted into third gear on the slope.
The shortstop threw the ball to third base.
三塁手 specifically means 'third baseman', whereas サード can refer to either the base, the position, or the player depending on context.
No language of origin is specified. The katakana form is used for English-like 'third' meanings in ordinal, baseball, and gear contexts.