The word 'Subtle' has many meanings depending on the context it is used in. Here they are talking about the language someone is using, so subtle in this context would imply that the person is making suggestions that are not obvious at first. The dictionary definition of Subtle is this: 1. not immediately obvious or comprehensible 2. difficult to detect or analyse, often through being delicate or highly refined: a subtle scent 3. showing or making or capable of showing or making fine distinctions of meaning Other words that you might use instead of Subtle are Sly, Tricky, Slick etc.

slight and not obvious. therefore difficult to notice.pleasantly delicate and understated