Tathāgata: the 'Perfect One', lit. the one who has 'thus gone', or 'thus come', is an epithet of the Buddha used by him when speaking of himself.

To the often asked questions, whether the Tathāgata still exists after death, or not, it is said (e.g. S. XXII, 85, 86) that, in the highest sense (paramattha, q.v.) the Tathāgata cannot, even at lifetime, be discovered, how much less after death, and that neither the 5 groups of existence (khandha, q.v.) are to be regarded as the Tathāgata, nor can the Tathāgata be found outside these corporeal and mental phenomena. The meaning intended here is that there exist only these ever-changing corporeal and mental phenomena, arising and vanishing from moment to moment, but no separate entity, no personality.

When the commentaries in this connection explain Tathāgata by 'living being' (satta), they mean to say that here the questioners are using the merely conventional expression, Tathāgata, in the sense of a really existing entity.

Cf. anattā, paramattha, puggala, jīva, satta.

 A commentarial treatise on "The Meaning of the Word 'Tathāgata' " is included in The All-Embracing Net of Views (Brahmajāla Sutta), tr. Bhikkhu Bodhi  (BPS).

Buddhist Dictionary, Manual of Buddhist Terms and Doctrines, by NYANATILOKA MAHATHERA

如來

Tathāgata

An epithet of the Buddha, used by the Buddha in referring to himself.

The Commentaries (DA.i.59-67; AA.i.58-63; MA.39-43; UdA.128ff., etc.) give eight (sometimes expanded to sixteen) explanations of the word, which shows that there was probably no fixed tradition on the point.

The explanations indicate that the name can be used for any arahant, and not necessarily only for a Buddha.

The term was evidently pre-Buddhistic, though it has not yet been found in any pre-Buddhistic work.

Dictionary of Pali Proper Names, G P Malalasekera (1899-1973), which is available as printed version from

tathāgata

(Sanskrit; Pāli). A title or epithet of the Buddha. The term can mean either ‘one who has thus come’ or ‘one who has thus gone’. The Buddha used the term to refer to himself after he had attained enlightenment (bodhi), and it became one of the stock epithets of a Buddha. Other honorific titles include Bhagavan (lord), Jina (conqueror), Arhat (worthy one), and Samyak-saṃbuddha (perfectly enlightened Buddha). The historical Buddha Siddhartha Gautama was also known as Śākyamuni or ‘the sage of the Śākyas’, and is commonly referred to this way in the Mahāyāna tradition.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)

tathāgata : [adj.] one who has gone so; the Enlighten One.

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

Tathāgata [Derivation uncertain. Buddhaghosa (DA i.59 -- 67) gives eight explanations showing that there was no fixed tradition on the point, and that he himself was in doubt]. The context shows that the word is an epithet of an Arahant, and that non -- Buddhists were supposed to know what it meant. The compilers of the Nikāyas must therefore have considered the expression as pre -- Buddhistic; but it has not yet been found in any pre -- Buddhistic work. Mrs. Rhys Davids (Dhs. tr. 1099, quoting Chalmers J.R.A.S. Jan., 1898) suggests "he who has won through to the truth." Had the early Buddhists invented a word with this meaning it would probably have been tathaŋgata, but not necessarily, for we have upadhī -- karoti as well as upadhiŋ karoti. -- D i.12, 27, 46, 63; ii.68, 103, 108, 115, 140, 142; iii.14, 24 sq., 32 sq., 115, 217, 264 sq., 273 sq.; S i.110 sq.; ii.222 sq.; iii.215; iv.127, 380 sq.; A i.286; ii.17, 25, 120; iii.35, etc.; Sn 236, 347, 467, 557, 1114; It 121 sq.; KhA 196; Ps i.121 sq.; Dhs 1099, 1117, 1234; Vbh 325 sq., 340, etc., etc.
   -- balāni (pl.) the supreme intellectual powers of a T. usually enumd as a set of ten: in detail at A v.33 sq. =Ps ii.174; M i.69; S ii.27; Nd2 466. Other sets of five at A iii.9; of six A iii.417 sq. (see bala); -- sāvaka a disciple of the T. D ii.142; A i.90; ii.4; iii.326 sq.; It 88; Sn p. 15.

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

如来名號

Entry Key: 3

【梵】tathāgataḥ
【梵】तथागतः【中】如來
【藏】de bzhin gshegs pa

 

Mahāvyutpatti - DDBC version

ta thA ga ta

[translation-san] tathāgata

[translation-eng] {Hopkins} [thus-gone] One Gone Thus [an epithet of the Buddha]

[comments] SW changed the entry to ""tathāgata"" from ""tathagata"".

Jeffrey Hopkins' Tibetan-Sanskrit-English Dictionary

de bzhin gshegs

[translation-san] tathāgata

[translation-san] {C} nararṣabha

[translation-eng] {Hopkins} [thus-gone]; One Gone Thus; epithet of the Buddha

[translation-eng] {C} the Great Bull; the mightiest of men

Jeffrey Hopkins' Tibetan-Sanskrit-English Dictionary

de bzhin gshegs pa

[translation-san] {C,MSA,MV} tathāgata

[translation-eng] {Hopkins} [thus-gone]; One Gone Thus; epithet of the Buddha

Jeffrey Hopkins' Tibetan-Sanskrit-English Dictionary

de bzhin bshegs pa

[translation-san] tathāgata

[translation-eng] {Hopkins} Tathāgata

Jeffrey Hopkins' Tibetan-Sanskrit-English Dictionary