名詞 lark:

1. North American songbirds having a yellow breast
   同義詞：meadowlark
2. a songbird that lives mainly on the ground in open country; has streaky brown plumage
   同義詞：pipit, titlark
3. any of numerous predominantly Old World birds noted for their singing
4. any carefree episode
   同義詞：escapade

動詞 lark:

1. play boisterously
   同義詞：frolic, rollick, skylark, disport, sport, cavort, gambol, frisk, romp, run around, lark about

1. She rose with the lark.
   她一大早就起床了。
2. He only said it for a lark.
   他只是說著玩而已。

lark

n.（名詞）
Any of various chiefly Old World birds of the family Alaudidae, especially the skylark, having a sustained, melodious song.
云雀：東半球百靈科鳴禽，尤指云雀，有持久婉轉(zhuǎn)的叫聲
Any of several similar birds, such as the meadowlark.
似云雀的鳥：相類似的小鳥，例如一種象草地鷚的小鳥

來源：
Middle English laveroc, larke
中古英語 laveroc, larke
from Old English l3werce
源自 古英語 l3werce

lark
lark 2

n.（名詞）
A carefree or spirited adventure.
嬉戲：指隨便或活躍的冒險
A harmless prank.
玩笑：指善意的惡作劇
v.intr.（不及物動詞）
larked,lark.ing,larks
To engage in spirited fun or merry pranks.
嬉戲：參與活潑的娛樂或善意的惡作劇

來源：
Perhaps short for skylark [to frolic]
可能為 skylark的簡寫[戲鬧]
and possibly alteration of dialectal lake [play] from Middle English leik, laik from Old Norse leikr
也可能是 方言 lake的變化 [玩] 源自 中古英語 leik, laik 源自 古斯堪的納維亞語 leikr

【引伸】
lark.er
n.（名詞）
lark.ish
adj.（形容詞）