uncircumcised, uncircumcision

Definition:

The terms "uncircumcised" and "uncircumcision" refer to a male who has not been physically circumcised. These terms are also used figuratively.

Egypt was a nation that also required circumcision. So when God talks about Egypt being defeated by the "uncircumcised," he is referring to people whom the Egyptians despised for not being circumcised.
The Bible refers to people who have an "uncircumcised heart" or who are "uncircumcised in heart." This a figurative way of saying that these people are not God's people, and are stubbornly disobedient to him.

If a word for circumcision is used or known in the language, "uncircumcised" could be translated as "not circumcised."
The expression "the uncircumcision" could be translated as "people who are not circumcised" or "people who do not belong to God," depending on the context.
Other ways to translate figurative senses of this term could include "not God's people" or "rebellious like those who don't belong to God" or "people who have no sign of belonging to God."
The expression "uncircumcised in heart" could be translated as "stubbornly rebellious" or "refusing to believe." However, if possible it is best to keep the expression or a similar one since spiritual circumcision is an important concept.