This phrase appears in the name of this Counter Strike video: http://www.youtube.com/watch?v=UTGisg5UPSE
1Стрим is nothing more than ‘[video] stream’. Донный is definitely a sort of negative way to describe it. Most probably it’s an adjective from Russian дно ‘bottom [of river, sea, some container]’.– Dmitry AlexandrovJul 20, 2014 at 20:57
1Yes, for sure it’s from дно. Дно (or even днище with augmentative suffix) in gamers’ slang is a word for calling a person who is extremely bad gamer or his style of game. See e. g. this thread on ‘World of Tanks’ forum.– Dmitry AlexandrovJul 20, 2014 at 21:08
Стрим is nothing more than ‘[video] stream’.
До́нный is regular adjective from дно́. And дно – literal ‘bottom [of river, sea or some container]’ – is also as an epithet for something like abyss of despair / despondency / poverty / etc (cf. Russian classic play by Maxim Gorky titled ‘На дне’).
But in gamers’ slang it somehow became a word for a person who is extremely bad gamer or his style of game.
A kind of Russian version of ‘Urbandictionary’ – teenslang.su – defines дно in this way:
Дно, -а, ср. (геймеры)
значение (1): оскорбление, попытка сказать что-то более страшное, чем слово нуб.
значение (2): в широком смысле — низшая степень чего-либо.
пример текста: Яша, ты дно, нах ты бару брал, если ты им никуя не умеешь.
Also you may take a look at for instance this thread on forum of ‘World of Tanks’ (popular MMORPG in ex-Soviet Union).
Дно in that meaning is no less common with augmentative suffix -ищ- – дни́ще. Even more strong but still common phrase is дни́ще ёбаное (mat, yes).
P. S. Now I found an article on Wikireality which explains the origin of term and says that it went beyond gamers’ slang, but it does not matter in a context of your question.