The raining, i.e. preaching, of the Mahāyāna. 

A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous

（喻）偉大的佛法能滋潤枯渴的眾生，好像雨水能潤澤大地一樣。

陳義孝編, 竺摩法師鑑定, 《佛學常見辭彙》

（譬喻）大法能慈潤枯渴之眾，故以譬於雨。法華經序品曰：「雨大法雨，吹大法螺。」同化城喻品曰：「普雨大法雨，度無量眾生。」

丁福保《佛學大辭典》

大法雨 (dà fǎ yŭ) 　( “the rain of the great Dharma” ) Cf. 法雨(fǎ yŭ) ;

{not found at 《漢語大詞典》2.1350.} ; {not found at 《大漢和辞典》3.439.} ;

Dharmarakṣa: {65c12} 今者，如來當敷大法，演無極典，散大法雨，擊大法鼓，吹大法螺，講無量法(p)

{K.16.11} mahā-dharmavṛṣṭi-

Kumārajīva: {L.3c13} 大法雨

A Digital Edition of A Glossary of Dharmarakṣa translation of the Lotus Sutra by Seishi Karashima, 1998

mahā-dharma-varṣa*.

佛教漢梵大辭典, 平川彰 Buddhist Chinese-Sanskrit Dictionary, Akira Hirakawa

P 736