httpd stands for Hypertext Transfer Protocol Daemon (i.e. web server).
The implied meaning can be:
- Apache HTTP Server
- CERN HTTPd HTTP server
- Cherokee HTTP server
- Hiawatha HTTP server with Reverse proxy functionality
- Lighttpd HTTP server
- NCSA HTTPd HTTP server
- Nginx HTTP and reverse proxy server
- Thttpd HTTP server
- TUX web server aka kHTTPd