SUBTLE is validvalid

so slight as to be difficult to detect [adj SUBTLER, SUBTLEST] : SUBTLENESS [n], SUBTLETY [n], SUBTLY [adv]

29,028 of 196,601 in NWL2023·also valid in CSW24

so slight as to be difficult to detect, also SUBTIL, SUBTILE [adj SUBTLER, SUBTLEST, SUBTLY]