名詞 dismount:

1. the act of dismounting (a horse or bike etc.)

動詞 dismount:

1. get off (a horse)
   同義詞：unhorse, light, get off, get down

1. I had to dismount from my bicycle halfway up the hill.
   我騎到半山腰只得從腳踏車上下來。
2. He who rides on a tiger can never dismount.
   [諺]騎虎難下。
3. One have to dismount from an idea and get into saddle again at every parenthesis.
   每當(dāng)遇上一個(gè)括號，就叫人不得不從一種想法下馬，然后再次騎上馬鞍。
4. Two soldiers dismounted the gun from the base.
   兩個(gè)戰(zhàn)士把炮從底座上卸下來。

dis.mount

v.（動詞）
dis.mount.ed,dis.mount.ing,dis.mounts
v.intr.（不及物動詞）
To get off or down, as from a horse or vehicle.
下馬，下車：離開或向下，如從馬或車輛上
v.tr.（及物動詞）
To remove from a support, setting, or mounting.
從支撐物、底板、底座取下，卸下
To unseat or throw off, as from a horse.
使下（馬），使掉下（馬）
To disassemble (a mechanism, for example).
拆開（機(jī)器等）
n.（名詞）

The act or manner of dismounting, especially from a horse.
摔下，下馬，下車：下來的動作或方式，尤指下馬
Sports A move in gymnastics whereby the gymnast gets off an apparatus or completes a floor exercise, typically landing on both feet.
【體育運(yùn)動】 下；下法：體操運(yùn)動中的一個(gè)動作，憑借這個(gè)動作，體操運(yùn)動員從鞍馬上跳下或完成自由體操運(yùn)動，一般是雙腳落地

來源：
Probably alteration of obsolete French desmonter [to unseat]
可能為 已廢法語 desmonter的變化 [使退位，使摔下馬]
des- [dis-]
des- [表示.除去，分離.的意思]
monter [to mount] * see mount
monter [騎上，登上] *參見 mount

【引伸】
dismount.able
adj.（形容詞）