A)*Noun* Pumpkin is a gourd-like squash of the genus Cucurbita and the family Cucurbitaceae (which also includes gourds).1
It is a common name of or can refer to cultivars of any one of the species Cucurbita pepo, Cucurbita mixta, Cucurbita maxima, and Cucurbita moschata. They are typically orange or yellow and have many creases running from the stem to the bottom. They have a thick shell on the outside, with seeds and pulp on the inside.
B)*Verb* Southern slang, to "pump-kin" or have sex with ones family member.
I carved a pumpkin last night.
I pumped my kin last night.