Said when someone is going too far with their actions and/or their opinions

The act of doing absolutely nothing but playing Halo Reach. Usually one "Reaches" instead of doing more important things like schoolwork or important dates.

the slang “reaching” can be used in a couple of ways. you’re able to use it when someone’s over exaggerating something to make it seem worse than what it actually was, or taking something too far.

When someone over-exaggerates facts to validate their own opinion

Action.
When somebody is taking something too far

to go somewhere.

The UNSC main military planet, close to earth, and suffered a sneak attack from the covenant.

reach, reachin, to go to. to be goin to i will go to. act of travel

Reach, or reaching is a synonym for come, coming, arrive, arriving, attend, attending etc.

It is often used in place of such phrases as: "Are you coming?", "Are you going\going to make it?", " Are you on your way?" in the interrogitive, and "Come over", "I'll be there", "I'm on the way" etc. in the exclamatory.
It often stands alone as the sole word in an (sms)text message.

Anecdotal evidence could lead one to believe that this unconventional, ambiguous usage of the word was introduced into the urban lexicon by homophobic, adolescent, or twenty-something wiggas, who possibly feared reprisal at the double entendre the words come and coming conjured in their cohorts, friends and\or homies.

Ultimately, and this is just a gut feeling, I believe the aforementioned (admittedly dubious) etymological origin story smacks of the clumsy and often extremely loose and liberal repurposing of words and phrases which have become commonplace in the post-www.\sms era of of the past few decades.

Said slanglish was probably first uttered by one young hip-hop sycophant to a friend, or acquaintance who probably had to ask for clarification as to its contextual meaning. Apparently, it was deemed either sufficiently cool and\or enough of a time\140 character saver when used as a single word in place of an entire sentence, that it managed to gain traction and be thusly co-opted and amalgamated into the lols and imhos of females aged 12-32...ensuring it's inclusion in the Urban Dictionary.