Dictionary Definition:
sādhu (adj.) [vedic sādhu, fr. sādh] 1. good, virtuous, pious sn 376, 393; j i.1; mhvs 37, 119; pva 116, 132; asādhu bad, wicked dh 163, 223; dha iii.313. -- 2. good, profitable, proficient, meritorious dh 35, 206 (=sundara, bhaddaka dha iii.271); d i.88; pv ii.97; nt. adv. well, thoroughly dh 67; j i.1; mhvs 36, 97; 37, 73. very frequent as interjection, denoting (a) request (adhortative, with imper.: sādhu gaccha please go! miln 18; gacchatha vva 305), to be translated with "come on, welcome, please," or similar adverbs. thus e. g. at pv iv.140 (=āyācane pva 232); j i.92; pva 6, 35, 272; vva 69; -- (b) assent & approval in replies to a question "alright, yes" or similarly; usually with the verbs (in ger.) paṭisuṇitvā, vatvā, sampaṭicchitvā etc. thus e. g. at j v.297; vin i.56; miln 7; dha iii.13; vva 149; da i.171; sna 176 (=sampahaŋsane); pva 55, 78 and passim.
-- kamyatā desire for proficiency vbha 477. -- kāra saying "well," approval, cheering, applause j i.223; miln 13, 16, 18; vva 132; dha i.390; iii.385. -- kīḷana a festive play, a sacred festivity mhvs 3, 11; sādhukīḷita the same mhvs 20, 36; ˚ -- divasa vin iii.285; sādhu -- kīḷā j iii.434; v.127; sādhu -- kīḷikā j iii.433. -- jīvin leading a virtuous life it 71. -- phala having wholesome fruits j i.272 (read sādu˚). -- rūpa good, respectable dh 262. -- sammata highly honoured d i.48; s iv.398; sn p. 90 sq.; miln 4, 21; da i.143. -- sīliya good character j ii.137.