intergrade

/ˌɪntərˈɡreɪd/
verb
  1. To change gradually from one form, type, or state to another, passing through intermediate stages.
    • The dialects intergrade across the border, making it hard to tell where one ends and the other begins.
    • In the painting, the colors intergrade smoothly from warm reds to cool blues.
    • The two species intergrade where their habitats meet, producing hybrids.
Antonyms
noun
  1. An intermediate form or stage in a gradual transition.
    • The fossil is an intergrade between two known species.
    • This plant is an intergrade between a shrub and a tree.
    • The dialect spoken here is an intergrade between northern and southern varieties.