There are 2 main definitions of suck up in English:

suck up1

informal Behave obsequiously, especially for one’s own advantage: he has risen to where he is mainly by sucking up to the president
More example sentences
  • After about a minute of sucking up and butterfly kisses, he gave in.
  • Every waiter and waitress sucks up as much as humanly possible, assuming that that's the way to earn a nice gratuity.
  • He sucks up to the fat cats; they wrinkle their noses and hand him the check using a pair of tongs.
Synonyms
grovel, creep, toady, be obsequious/servile/sycophantic, kowtow, bow and scrape, play up, truckle;
fawn on, curry favour with, dance attendance on
informal bootlick, lick someone's boots, be all over, fall all over, butter up, rub up the right way, keep sweet
British vulgar slang lick/kiss someone's arse
See parent entry: suck

Definition of suck up in:

There are 2 main definitions of suck up in English:

suck-up2

Line breaks: suck-up

noun

North American informal
A person who behaves obsequiously, especially for their own advantage.
More example sentences
  • So after vetting the list to weed out any cantankerous curmudgeons, the candidate pool will consist of mainstream hacks, true believers and morally rancid suck-ups to political authority.
  • Well now, I didn't want to look like too much of a suck-up, so I only agreed ‘strongly’ rather than ‘totally’.
  • I'm not saying I hate all preps, but these were the super-annoying suck-ups.

Definition of suck up in: