/ ʌnˈtruː; NAmE / adjective
1.
not true; not based on facts :
These accusations are totally untrue.
an untrue claim
It is untrue to say that something like this could never happen again.
2.
untrue (to sb/sth) ( formal ) not loyal to sb/sth
SYN unfaithful :
If he agreed to their demands, he would have to be untrue to his own principles.
OPP true
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WORD ORIGIN
Old English untrēowe unfaithful (see un- , true ).