1sneak 
/ˈsni:k/ verb
sneaks; sneaked or chiefly US snuck /ˈsni:k/ verb /ˈsnʌk/; sneak·ing 1 always followed by an adverb or preposition [no obj] : to move quietly and secretly in order to avoid being noticed
▪ They tried to sneak into the movie without paying. ▪ As a teenager she would sneak out (of her house/apartment) at night to visit her boyfriend. ▪ He sneaked [=crept] past the guard. 2 [+ obj] : to take or bring (something) secretly and often quickly
▪ She sneaked some cigars through customs. ▪ He snuck a few cookies out of the jar while his mother wasn't looking. ▪ They caught him trying to sneak food into the theater. ▪ I sneaked a note to my friend in class. = I sneaked my friend a note in class. ▪ I'm going to sneak a smoke. [=I'm going to smoke a cigarette while nobody is watching] ▪ I was caught sneaking a look [=secretly looking] at my Christmas presents. ▪ Can I sneak a peek at your quiz answers? 3 [no obj] Brit, old-fashioned : to tell someone (such as a parent or teacher) about something wrong that someone else has done
▪ I got in trouble after she sneaked [=squealed, (chiefly US) tattled] on me.
▪ They tried to sneak into the movie without paying. ▪ As a teenager she would sneak out (of her house/apartment) at night to visit her boyfriend. ▪ He sneaked [=crept] past the guard.
▪ She sneaked some cigars through customs. ▪ He snuck a few cookies out of the jar while his mother wasn't looking. ▪ They caught him trying to sneak food into the theater. ▪ I sneaked a note to my friend in class. = I sneaked my friend a note in class. ▪ I'm going to sneak a smoke. [=I'm going to smoke a cigarette while nobody is watching] ▪ I was caught sneaking a look [=secretly looking] at my Christmas presents. ▪ Can I sneak a peek at your quiz answers?
▪ I got in trouble after she sneaked [=squealed, (chiefly US) tattled] on me.
sneak up on [phrasal verb]
sneak up on (someone) 1 : to approach (someone) quietly and secretly in order to avoid being noticed
▪ My father likes to sneak up on my mother and tickle her. ▪ Don't sneak up on me like that! 2 : to approach, happen, or develop without being noticed
▪ My birthday really snuck up on me this year. ▪ This kind of problem can sneak up on you if you're not attentive.
▪ My father likes to sneak up on my mother and tickle her. ▪ Don't sneak up on me like that!
▪ My birthday really snuck up on me this year. ▪ This kind of problem can sneak up on you if you're not attentive.
