Longterm forecasts were largely a matter of guesswork.是什么意思？

Longterm forecasts were largely a matter of guesswork.

远期预测在很大程度上是一种猜测。

forecasts

n. 预测，预报( forecast的名词复数 )；v. 预言，预报( forecast的第三人称单数 )；

例句
Local radio stations serving coastal areas often broadcast forecasts for yachtsmen...
服务沿海地区的地方广播电台经常为驾驶游艇出海的人播报天气预报。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

largely

adv. 大部分地，主要地，大规模地，丰富地；

例句
...a research programme that has largely failed to achieve its principal aims.
在较大程度上未能实现其主要目标的研究项目

matter

n. 事件，（讨论、考虑等的）问题，重要性，物质；vi. 要紧，重要，化脓，有重大影响，有重要性；

例句
The matter was left in abeyance until Haig saw French.
事情被搁置了起来，直到黑格见到法国人。

of

prep. 关于，属于…的，由…制成；aux. 助动词 [非标准用语、方言] =have [主用于虚拟语气]；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

guesswork

n. 猜想，猜测；

例句
It was pure guesswork on our part.
这纯属我们的猜测。