It's simply called a palindromic sequence.
As you can see here, these sequences are called inverted repeats when random nucleotides are found between the initial sequence and its reverse complement (e.g. TTACGnnnnnnCGTAA), while when there are no nucleotides between them they're called palindromes.
Sorry for my previous answer, I must've missed ...
As an example of biological symmetry, with my tongue in my cheek, I would call this a mirage.
My reason is that from a structural point of view a sequence of the type you present:
5'... ATGCC|CCGTA ...3'
3'... TACGG|GGCAT ...5'
does not have mirror-image symmetry. This lack of symmetry is because of the asymmetric nature of the phosphodiester bond. The 5'...