Culminating means to reach the highest or greatest point; in astrology this usually refers to the arrival of a planet at the midheaven, though the term was also used in ancient astrology to refer to planets reaching the IC, where they were described as “culminating beneath the earth”.
Culpeper, Nicholas - astrologer (1616 - 1654)
Younger associate of William Lilly, Culpeper became a legendary figure in the history of herbal medicine. A political radical, he ignored the monopoly held by the Royal College of Physicians and wrote his books in English, to make medical knowledge freely available to everyone. He is best known for his English Physician (1653), now known as Culpeper’s Herbal, which integrated theories of the doctrine of signatures and astrology into herbal medicine and became one of the most widely circulated texts in publishing history. His Astrological Judgement of Diseases from the Decumbiture of the Sick, published posthumously in 1655, gives a more detailed account of astrological techniques for treating illness.
The cusps are the dividing lines between one house (or sign) and the next. Planets close to house cusps are considered to have more powerful influences than those removed from the cusps.