1. (a.) Infinitely or indefinitely small; less than any assignable quantity or value; very small.

2. (n.) An infinitely small quantity; that which is less than any assignable quantity.

atomic corpuscular embryonic evanescent germinal granular impalpable imperceptible imponderable inappreciable indiscernible intangible invisible microcosmic microscopic molecular subatomic tenuous thin ultramicroscopic unseeable