underthreshold

From under- +‎ threshold, probably a calque of German unterschwellig (“subliminal”, literally “under-threshold”), from unter- (“under-”) + Schwelle (“threshold”). More at under, sill.

underthreshold (comparative more underthreshold, superlative most underthreshold)

1. Positioned below a threshold.
2. Being below the threshold or outside of the ordinary limits of consciousness; subconscious; subliminal.
   • 1913, Edward Ebenezer Weaver, Mind and health:

     The notion "underthreshold" is to be explained as all that which is under the ordinary threshold or outside the customary bounds of consciousness; [...]

   • 1986, Hormonal ensemble in exercise:

     Accordingly, it represents an underthreshold load in trained persons, and no endocrine response was observed.

   • 2003, Vincenzo Capasso, Mathematical modelling & computing in biology and medicine:

     In this way it is possible to describe the underthreshold membrane behavior of a neuron distinguishing the effects of synapses located in the main dendritic tree or near the trigger zone.