叩く

to strike; to hit; to beat; to knock; to pound; to bang; to slap; to spank; to tap; to pat; to clap (one's hands); to play (the drums)

to attack; to bash; to criticize; to censure; to flame (on the Internet)

to sound out (someone's views)

to pound (meat or fish); to chop into small pieces

to beat down the price

to talk (big, bad, idly, etc.)

as ...口を叩く

to call; to invoke (e.g. a function)