維基百科上的解釋：
Operational definition中有這樣一段：
if it walks like a duck and quacks like a duck,it must be some kind of duck,may be regarded as involving a sort of measurement process or set of tests (see duck test)
樓上各位對于原句的翻譯都是對的,我就不再翻譯了,除了這句：
may be regarded as involving a sort of measurement process or set of tests
可以被看作是涉及到一種測量過程或測試（參見duck test）
于是我轉(zhuǎn)到duck test,有這樣的解釋：
The duck test is a humorous term for a form of inductive reasoning.
鴨子的測試是歸納推理的一種幽默的說法.
This is its usual expression:
“If it looks like a duck,swims like a duck,and quacks like a duck,then it probably is a duck.”
The test implies that a person can identify an unknown subject by observing that subject's habitual characteristics.It is sometimes used to counter abstruse arguments that something is not what it appears to be.
這個測試意味著一個人可以通過觀察主體的習慣性的特點來鑒別未知主體.它有時被用來反駁“某物的實質(zhì)其實并不是它表面所呈現(xiàn)的那樣”這樣一種令人費解的深奧的觀點.
現(xiàn)在你應該理解了.不明白可以再聯(lián)系我.