人跨坐在東西上
這一支就是核心畫面本身：真的有一雙腿，真的分在兩邊。
r · C1
Sitting or standing over something with one leg on each side of it, the way you sit on a horse or a bicycle.
跨坐；跨立
核心畫面
One way to picture astride: someone is in the middle of a long step, one leg in front and one behind, and they stop there with the legs still apart. Lower the body a little and whatever is underneath is now between the two legs. That is the whole word — one leg on each side.
astride 可以想成一個人正跨著一大步，一腳在前一腳在後，然後停住，腿還張著。把身體放低一點，中間那樣東西就被兩…更多收起
astride 可以想成一個人正跨著一大步，一腳在前一腳在後，然後停住，腿還張著。把身體放低一點，中間那樣東西就被兩腿夾住了。這就是整個字要說的事：一邊一隻腳，東西在中間。這個畫面後來被放大到地圖上——身體換成城鎮，中間那樣東西換成一條河。姿勢沒有變，只是尺寸變了。From the word’s history
Formed from a- plus stride, the long step you take when walking.
astride 由 a- 加上 stride（跨步）組成。stride 是走路時跨出去的那一大步，astride 則是停在那個跨開的狀態上。
Wiktionary etymology supplied in this packet (source_ref kaikki:3f6f69a190036ae4:748111602)
Two branches
地方橫跨兩邊
把身體換成城鎮或農場，把馬換成河或邊界，同一個姿勢就變成地圖上的位置。
r · C1
Placed so that it reaches or covers both sides of a river, road, border or similar line.
橫跨；分立兩側