without apparent forethought or prompting or planning; "an unplanned economy"; "accepts an unplanned order"; "an unplanned pregnancy"; "unplanned remarks"
derived from experiment and observation rather than theory; "an empirical basis for an ethical theory"; "empirical laws"; "empirical data"; "an empirical treatment of a disease about which little is known"
not capable of being precisely or readily described; not easily put into words; "an indefinable feeling of terror"; "an abstract concept that seems indefinable"
defying expression or description; "indefinable yearnings"; "indescribable beauty"; "ineffable ecstasy"; "inexpressible anguish"; "unspeakable happiness"; "unutterable contempt"; "a thing of untellable splendor"