The classical term described the patient who forgets sessions, changes the subject, arrives late or rejects interpretations. The framing was that they were defending against awareness, and the therapist's task was to overcome the defence.
Practice has moved considerably. William Miller and Stephen Rollnick's work on motivational interviewing showed that what was called resistance rises or falls depending on what the therapist does: confrontation measurably amplifies it, reflective listening reduces it. In an often-cited study, therapist style predicted the patient's drinking a year later.
The useful reframing: resistance is ambivalence, and ambivalence is normal. Anyone who wants to change also has reasons to stay the same — otherwise they would have changed already. A pattern that persists usually does something for the person, and that something is worth understanding before being fought.
Practically, resistance is information about three things: the pace is too fast, safety is insufficient, or the method does not fit. All three are open to discussion — and anyone who feels they are resisting their own therapy almost always has a reason worth saying out loud.