See niche in Webster's New World College Dictionary
noun
a recess or hollow in a wall, as for a statue, bust, or vase
a place or position particularly suitable to the person or thing in it
any small, specialized business market
Ecol.
the particular role of an individual species or organism in its community and its environment, including its position in the food cycle and its behavior
the specific space occupied by an organism within its habitat
A recess in a wall, as for holding a statue or urn.
A cranny, hollow, or crevice, as in rock.
a. A situation or activity specially suited to a person's interests, abilities, or nature: found her niche in life.
b. A special area of demand for a product or service: “One niche that is approaching mass-market proportions is held by regional magazines”(Brad Edmondson).
Ecology
a. The function or position of an organism or population within an ecological community.
b. The particular area within a habitat occupied by an organism.