ratchet

詳細解釋：

ratch.et

n.（名詞）
A mechanism consisting of a pawl that engages the sloping teeth of a wheel or bar, permitting motion in one direction only.
棘輪，棘爪：一種包含合於轉輪或長條傾斜性齒輪中的爪狀物的機械，使輪僅向一個方向運動
The pawl, wheel, or bar of this mechanism.
棘輪，棘爪，棘條：這種機械裝置中的爪狀物，轉輪或長條
v.tr.（及物動詞）
ratch.et.ed,ratch.et.ing,ratch.ets
To increase or decrease by increments. Often used withup, upward, down, or downward :
漸進：一步步地增加或減少。通常與up,upward,down 或 downward 一起使用：
例句：
.Some companies . . . may make things worse if they seek to ratchet down their medical expenses by limiting benefits for psychological or psychiatric care.(Newsweek)
.有些公司企圖限制精神或心理衛生上的福利來減少醫療開支，那它們只會把事情搞得更糟.(新聞周刊)

來源：
French rochet
法文 rochet
from Old French rocquet [head of a lance (from the shape of the teeth)]
源自 古法文 rocquet [長矛尖端（由齒狀而來）]
[of Germanic origin]
[來源於德文]