Final answer:
Live Drawing Comedy combines the immediacy of artistic drawing with an interactive, humorous performance that engages an audience. This form of art emphasizes the process and the performer's skillful interaction with spectators.
Step-by-step explanation:
The activity described in the student's question, where an artist performs live in front of an audience, drawing caricatures and portraits with rapidity and often with a humorous twist, can best be defined as Live Drawing Comedy. This form of art combines the immediacy of sketching with the interactive and performative elements of theater, as the artist may engage directly with the audience for subject suggestions. It emphasizes the artistic skill of the performer and the entertainment value of the process, rather than just the outcome of the drawing itself. Prominent examples of the use of drawing in performance art can be seen in Marina Abramovic's 'The Artist is Present', where the performance and the artist's interaction with the audience are central to the experience.