It refers to the act of giving yet providing nothing of substance in return, as it is named after the parasitic organism a leech.

Leecher can be applied practially to peer to peer file sharing protocols, or networks (Bittorrent, Kazza Fast Track, Gnutella}, in which the leecher consumes bandwidth by downloading, yet has no will to upload or give back to a community.

Particularly in Bittorrent, leechers are not actually increasing their performance, but possibly are decreasing it.
I know a leecher who in order to acheive maximum network thourough-output restricts uploading while bittorrenting.
by Indrid Cold August 9, 2004
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A leecher is a person on some type of internet community (torrent, forums, ect.) who downloads as they please and never contributes back to that community. Often characterized by low post counts or having nothing in their shared folder. Leechers steal a network's bandwidth with downloads and potentially can cause it to lag. Derived (obviously) from the parasite with many similarities to a Leecher.
{18:43} <&Shade> Aero, click the members link in the forums!
{18:44} <&Aeroadm> Why?
{18:44} <&Shade> I did the math, only 3% of the members have posted more than 10 times!
{18:44} <&Aeroadm> leechers....
{18:44} <&Shade> Yea, yo DL! Delete those SOB leechers!
{18:45} <~Dark_Llama>Wha? Nah man, They boost the member counts :P
{18:45} <&Shade> -_-
{18:45} <&Aeroadm> -_-
by The Real Shade April 19, 2006
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Someone who takes a lot and doesn't give much
Dang, Bob leeched me 10 cigs at the party and he had a full pack!
by xSmurf June 20, 2004
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Leeching is when you download via a torrent or any other intarweb shareprogram, without giving any upload back.

leeching is especially harmfull to the bittorrent network (sucking all the bandwith away)
fucking hell! the Half life 2 torrent is full of leechers!!1!!1
by Superdude November 23, 2004
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Someone who acts so cool like a programmer, but is indeed just using his Copy-And-Paste ability, taking code from the Web without helping others. If he can't finish something on his own, he'll begin spamming all forums for an answer... and then will release his "own" application.
Someone whose abilities are usually not so good, and keeps exploiting someone else's effort without any Care-To-Share his code
He's not a programmer, he's just a leecher
by ZheCk April 17, 2007
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noun; unwanted friend who leeches all of your other friends. when one friend has a good catch-phrase or joke the leecher jumps all over it and takes it for himself/herself.

I told this joke about giving a nasty dragon and the next day i hear dumbass say the same one. What a fuckin leecher.
by MIKEYW October 3, 2006
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an asshole who will take some hits when he didnt even throw up some coin.
Ronny is such a fuckin leecher, he wasted my chronic.
by watts9111 August 1, 2008
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