Wordnet 3.0
NOUN (2)
1. 
 someone who controls access to something; 
- Example: "there are too many gatekeepers between the field officers and the chief"2. 
 someone who guards an entrance; 
[syn: doorkeeper, doorman, door guard, hall porter, porter, gatekeeper, ostiary]
WordNet (r) 3.0 (2006):
gatekeeper
    n 1: someone who controls access to something; "there are too
         many gatekeepers between the field officers and the chief"
    2: someone who guards an entrance [syn: doorkeeper, doorman,
       door guard, hall porter, porter, gatekeeper,
       ostiary]