Active

In the minimalism, a category X is active if it contains an uninterpretable feature F (an attractor). This feature turns X into a probe which seeks a matching goal, i.e. a category Y with a matching (e.g. identical or non-distinct) feature F’. Matching of probe-goal induces Agree, a relation eliminating the uninterpretable features activating the probe and the goal.

Link
Utrecht Lexicon of Linguistics