Certainly not as a very strong expression in Greek and is used in the Septuagint in Ezekiel 4.14 where Revised Standard Version has “never.”

The Good News Translation has added to the adjectives defiled and unclean the qualifier considered (see also the verb consider anything unclean in v. 15) because Peter is referring to the Jewish religion which considered certain animals clean and others unclean. The introduction of the term considered is particularly important, for defiled or unclean do not characterize the animals in a literal sense, but obviously in the religious context. The equivalent of defiled is often “impure” or “bad,” but not in the sense of behavior. A term such as “contaminated” may also be employed. A term for unclean must not be understood merely in the sense of “dirty”; rather, the meaning is “not fit to be eaten” or “not such that one should eat.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .