Of the nature of a passage or transition; transitional.

Characterized by or involving transition (in various senses); †that has something passing through it (obsolete); esp. that is in an intermediate…

Of or relating to transition; characterized by or involving transition or change; intermediate.

Of or relating to transition; characterized by or involving transition or change; intermediate; = transitional, adj. a.

Of a process: Taking place by degrees; advancing step by step; slowly progressive. Of a slope: Gentle, not steep or abrupt.

Advancing by grades or steps.

Pertaining to, or characterized by, gradation.

(un-, prefix1 affix 1.)

Characterized by being on a boundary or threshold, esp. by being transitional or intermediate between two states, situations, etc.