to set (a boat or ship) afloat
to release or send off (e.g. a rocket)
to start or set (something or somebody) in motion, e.g. on a course or career
I take any lady whose conduct is shady … and launch her in first-rate society — W S Gilbert
to introduce (a new product) onto the market
a party to launch a new book
to throw (oneself) forward
She launched herself at the player's legs
(+ into) to begin to do something energetically and with commitment
He launched into a rendition of his favourite pop song
[Middle English launchen to hurl a missile, via French lancher from late Latin lanceare to wield a lance]