[1] The word pollinator is often used when pollenizer is more precise.
A pollinator is the biotic agent that moves the pollen, such as bees, moths, bats, and birds.
While some plants are capable of self-pollenization, pollenizer is more often used in pollination management for a plant that provides abundant, compatible, and viable pollen at the same flowering time as the pollinated plant.
For example, most crabapple varieties are good pollenizers for any apple tree that blooms at the same time, and are often used in apple orchards for the purpose.
A pollenizer can also be the male plant in dioecious species (where entire plants are of a single sex), such as with kiwifruit or holly.