一下儿的英文：
a little bit
a little while

参考例句：

You may, out of politeness, nod your head, or say hello to the speaker.
你可以出于礼貌，点一下儿头，或者问一声好，就可以了。

`So did I, madam, and I am excessively disappointed
“我也是的，夫人，您看我这一下儿真给弄得狼狈极了。

little是什么意思：
adj. 小的；年幼的；短的，近的；可爱的；讨厌的；微不足道的
pron. 不多的；一些
adv. 少许；稍微
n. 少许；没有多少；短时间

He is recovering little by little.
他的健康正在渐渐地恢复起来。

Little by little and Bit by Bit
积少成多,积沙成塔

What costs little is little esteemed.
便宜的东西得不到珍视。

A little bird is content with a little nest.
小鸟满足于小巢。

Profound knowledge is accumulated little by little.
渊博的知识是逐渐积累起来的。

bit是什么意思：
n. 一点；少量；钻头
v. 约束；给（马）上嚼口

Little by little and Bit by Bit
积少成多,积沙成塔

The collective wealth has been accumulated bit by bit.
集体的家业是一点一滴地积攒起来的。

A rabid dog bit him.
他被一只疯狗咬了。

She's a bit of a mystery!
她这人有点来历不明！

a bit of; a scrap of; a stitch of
一点点