adj. Relating to a beginning or first stage of a process; inceptive; inchoative; marginal; insignificant.
the GNU version of the Collaborative International Dictionary of English
adj. of or pertaining to a limen, especially a sensory threshhold.
adj. marginally perceptible.
The Century Dictionary and Cyclopedia
Pertaining to the threshold or entrance; hence, relating to the beginning or first stage; inceptive; inchoative.
Specifically In psychophysics, pertaiuing to the stimulus limen or differential limen. See limen.
Word Usage
"Dragonflies tend to turn up at times in my life that I would describe as liminal -- threshold moments when you stand in the doorway between what your life was before and what it will be."