garu : [adj.] heavy; serious; grave; venerable; honoured. (m.), a teacher; instructor.

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]

Garu [Vedic guru; Gr. baru/s, Lat. gravis & brutus, Goth. kaurus] 1. adj. (a) lit. heavy, opp. lahu light, appld to bhāra, a load S iii.26; J i.196 (=bhārika); vi.420; DhA i.48; Sdhp 494 (rūpagarubhāra the heavy load of "form"). Compar. garutara (as against Sk. garīyaŋ) PvA 191. -- (b) fig. important, to be esteemed, valued or valuable A iii.110 sq. (piya manāpa g. bhavanīya); c. gen. or -- ˚ bent on (often in sequence ˚garu, ˚ninna, ˚poṇa, etc., e. g. Vism 135); pursuing, paying homage to, reverent; (or) esteemed by, honoured, venerated: Satthugaru esteeming the Lord; Dhamma˚, Sanghe g. A iii.331=iv.28 sq.; dosa˚ S i.24; kodha˚, saddhamma˚ (pursuing, fostering) A ii.46 sq.=84 sq.; Sdhp 1 (sabba -- loka˚ worshipped by all the world); Dpvs iv.12. -- agaru (c. gen.) irreverent towards Sn p. 51 (Gotamassa). Cp. garuka, gārava; also agaru & agalu. -- 2. N. a venerable person, a teacher: garunaŋ dassanāya & sakāsaŋ Sn 325, 326 (v. l. garūnaŋ to be preferred, so also SnA 332, 333); garūnaŋ dārā It 36. -- garukaroti (for garuŋ k˚) to esteem, respect, honour; usually in series sakkaroti g˚ māneti pūjeti Vin ii.162; M i.31; D i.91; A iii.76; iv.276; Nd2 334 (on namati), 530 (on yasassin); PvA 54. Expl. at DA i.256 by gāravaŋ karoti. -- garukātabba worthy of esteem PvA 9. -- garukāra (sakkāra g. mānana vandana) esteem, honour, regard Pug 19=Dhs 1121. -- See also guru.
   -- upanissita (adj.) depending on a teacher, one being taught Ps ii.202; -- ṭṭhāniya one who takes the place of a teacher A iii.21, 393; Nett 8; Vism 344. -- dhamma a rule to be observed. There are 8 chief rules enum. at Vin ii.255=A iv.276, 280; see also Vin iv.51, 315; v.136. Taken in the sense of a violation of these rules Vin i.49=ii.226; i.52, 143, 144; ii.279; -- nissaya in ˚ŋ gaṇhāti to take up dependency on a teacher, i. e. to consider oneself a pupil Vin ii.303; -- saŋvasa association with a teacher Nd2 235 4˚; Miln 408.

Pali-English Dictionary, TW Rhys Davids, William Stede,

garu: a. 重(ㄓㄨㄥˋ)

巴漢辭典 編者：(斗六) 廖文燦

garu for guru in agaru, q.v
 

Sanskrit-English Dictionary, by M. Monier William