(tropical:) A day [of clouds] bursting, or opening vehemently, with rain. (A.)
2.
الحُرُوفُالمُنْفَتِحَةُ (assumed tropical:) The letters of which the utterance requires the opening of [that part of the mouth which is called] theحَنَك; (TA;) all the letters of the alphabet exceptص, ض, ط, andظ. (K, TA.)