Quick Definition
a sea monster, huge fish
Strong's Definition
a huge fish (as gaping for prey)
Derivation: probably from the base of G5490 (χάσμα);
KJV Usage: whale
Thayer's Greek Lexicon
κῆτος, κητεος (κήτους), τό, a sea-monster, whale, huge fish (Homer, Aristotle, others): Mat_12:40, from Jon_2:1 where the Sept., κήτει μεγάλῳ for βΘΜγεμ γΗΜβ.
Mounce Concise Greek Dictionary
κῆτος kētos 1x
a large fish, sea monster, whale, Mat_12:40
Abbott-Smith Greek Lexicon
κῆτος , -εος (-ους ), τό ,
[in LXX : Jon_2:1 ; Jon_2:10 ( H1709 ) Gen_1:21 ( H8577 ), etc.;]
a huge fish, sea-monster: Mat_12:40 ( LXX ).†
Liddell-Scott — Intermediate Greek Lexicon
κῆτος κῆτος, εος, "any sea-monster or huge fish", Hom. , Hdt. "an abyss, hollow", cf. κητώεις.
STEPBible — Tyndale Abridged Greek Lexicon
κῆτος, -εος (-ους), τό
[in LXX: Jon.2.1; Jon.2.10 (דָּג) Gen.1:21 (תַּנִּין), etc. ;]
a huge fish, sea-monster: Mat.12:40 (LXX).†
(AS)