Oxford Advanced American Dictionary

Definition of onto preposition from the Oxford Advanced Learner's Dictionary

 Oxford3000

onto

preposition
onto pronunciation English ˈɒntə onto pronunciation American ˈɑːntə onto pronunciation American ˈɔːntə before vowelsonto pronunciation English ˈɒntu onto pronunciation American ˈɑːntu onto pronunciation American ˈɔːntu
(also on to)
 
1 used with verbs to express movement on or to a particular place or positionMove the books onto the second shelf.She stepped down from the train onto the platform.2 used to show that something faces in a particular directionThe window looked out onto the terrace.
Phrasal verbs

be onto somebody

1 (informal) to know about what somebody has done wrongShe knew the police would be onto them.2 to be talking to somebody, usually in order to ask or tell them somethingThey've been onto me for ages to get a job.

be onto something

to know about something or be in a situation that could lead to a good result for youScientists believe they are onto something big.She's onto a good thing with that new job.