For me it's using one language in a non-idiomatic manner because your approach to solving problems has been pushed in one direction by another languages idioms.
If the idioms you choose to use are typical of one language, you're coding with an accent. If the idioms you choose to use are common to a lot of languages, but the language you're using has a "better way", you're coding in baby talk, which is different from an accent. In other words, if it's clear that your background is with a particular language, you're coding with an accent; if it's only clear that your background isn't
with the language you're using, no accent.
Caution: Contents may have been coded under pressure.