I can't find a second meaning.
I think in this case, it's "Manhattan" for the sake of it being Manhattan as mentioned in bin Laden's speeches and his obsession with New York in general.
****
The following are excerpts from Osama bin Laden's speech on the eve of the 2004 US elections:
Osama bin Laden: Oh the American people, I address these words to you regarding the optimal manner of avoiding another Manhattan, and regarding the war, its causes and its consequences. But before this, I say to you: Security is one of the important pillars of human life, and free men do not take their security lightly, contrary to Bush's claim that we hate freedom. Let him explain why we did not attack Sweden, for example. Clearly, those who hate freedom have no pride, unlike the 19, may Allah have mercy on them. We have been fighting you because we are free men who do not remain silent in the face of injustice. We want to restore our [Islamic] nation's freedom. Just as you violate our security, we violate yours. (snip)
http://www.memritv.org/Transcript.asp?P1=312
From nwg post from the NY Post.
[If I read this correctly, the chemists were coming to meet 19 already here] snip
The terrorists were described as unemployed chemists who had recently taken a six-week explosive training course in Afghanistan.
The al Qaeda snitches also told U.S. officials that they planned to travel to New York, by way of Syria, with bogus passports.
Once here, they would meet up with 19 operatives who had already been sent to New York to help set off the bombs, the sources said.
The bombs would either be hidden in baby carriages or planted in briefcases similar to those used in this summer's London bus and train bombings.
Bloomberg said the FBI notified the city of the threat in recent days.
NBC News agreed Tuesday to withhold reporting about the plot in order to allow the investigation to proceed.
But Homeland Security Department officials downplayed the threat.
Department spokesman Russ Knocke refused to explain why it was discrediting the tip — or to comment on whether it had originated with the al Qaeda operatives arrested in Iraq.
An official who was briefed on the plot said the threat was considered doubtful because it did not reflect "detailed, pre-surveillance," but information that could be found on the Internet.
snip~
Regional FBI Director Mark Mershon, who appeared with Bloomberg and Kelly at a news conference, said that "classified operatives" had "partially disrupted this threat" and added that "multiple individuals are involved."
LINK