underground underground /ˈʌndɝˌgraʊnd/

adjective

1. () Under the level of the ground  ( belowground , underground )
   under the level of the ground
    Belowground storage areas
   belowground storage areas
    Underground caverns
   underground caverns
   
2. Conducted with or marked by hidden aims or methods  ( cloak-and-dagger , hole-and-corner , hugger-mugger , clandestine , hush-hush , secret , surreptitious , undercover , underground )
   conducted with or marked by hidden aims or methods
    Clandestine intelligence operations
   clandestine intelligence operations
    Cloak-and-dagger activities behind enemy lines
   cloak-and-dagger activities behind enemy lines
    Hole-and-corner intrigue
   hole-and-corner intrigue
    Secret missions
   secret missions
    A secret agent
   a secret agent
    Secret sales of arms
   secret sales of arms
    Surreptitious mobilization of troops
   surreptitious mobilization of troops
    An undercover investigation
   an undercover investigation
    Underground resistance
   underground resistance
   

adverb

1. Beneath the surface of the earth  ( underground )
   beneath the surface of the earth
    Water flowing underground
   water flowing underground
   
2. In or into hiding or secret operation  ( underground )
   in or into hiding or secret operation
    The organization was driven underground
   the organization was driven underground
   

noun

1. [British] An electric railway operating below the surface of the ground (usually in a city)  ( subway system [ N. American] , tube [UK] , underground [British] , metro , subway [ N. American] )
   an electric railway operating below the surface of the ground (usually in a city)
    In Paris the subway system is called the metro' and in London it is called the tube' or the underground'
   in Paris the subway system is called the metro' and in London it is called the tube' or the underground'
   
   
2. A secret group organized to overthrow a government or occupation force  ( resistance , underground )
   a secret group organized to overthrow a government or occupation force
   

 milepost milepost /ˈmaɪlˌpoʊst/

noun

1. Stone post at side of a road to show distances  ( milepost , milestone )
   stone post at side of a road to show distances
    We passed a milestone indicating we were 50 miles from the next city.
   We passed a milestone indicating we were 50 miles from the next city.
   
   

 receipt receipt /riːˈsiːt/

noun

1. () The act of receiving  ( reception , receipt )
   the act of receiving
    The reception was bustling with activity as guests checked in and out
   The reception was bustling with activity as guests checked in and out
   
2. () An acknowledgment (usually tangible) that payment has been made  ( receipt )
   an acknowledgment (usually tangible) that payment has been made
    The waiter brought the receipt with a pen for me to sign at the end of the meal
   The waiter brought the receipt with a pen for me to sign at the end of the meal
   
   

verb

1. Mark or stamp as paid  ( receipt )
   mark or stamp as paid
   
2. Report the receipt of  ( receipt , acknowledge )
   report the receipt of
    The program committee acknowledged the submission of the authors of the paper
   The program committee acknowledged the submission of the authors of the paper
   

 genus Piper genus Piper /ˈdʒiːnəs ˈpaɪpər/

noun

1. Type genus of the Piperaceae: large genus of chiefly climbing tropical shrubs  ( genus Piper , Piper )
   type genus of the Piperaceae: large genus of chiefly climbing tropical shrubs