I looked up in the dictionary, there are 12 meanings for it!
Just wonder when to use which for “大概”? Are there any words with the same meaning?
I think these other answers are more harmful than they are helpful and here's why: none of them have addressed how 大概 is applied in the real context of using the language. Anyone can look up a word in the dictionary and copy/paste the results here. OP's question is what does 大概 really mean (aka how is it used) and is there anything else like it?
大概 is generally used to mean "approximately", "more or less", or "something like that". Here's an example:
我大概明白你的意思。
What this sentence is saying is: "I don't understand what you're saying completely but I get the gist."
And another:
A：你打了多少个电话？ (How many phone calls did you make?)
B：大概50个。(Approximately 50.)
In terms of other words that capture a similar meaning, the closest approximation I can think of is 左右. Here's how this word could be applied to the example above:
B：50个左右。(50 or thereabouts.)
Here's another example of how using 大概 and 左右 are approximately the same but have a different connotation:
A：你的车买了多少钱？
B1: 大概三十万人民币。(Around 300,000RMB.)
B2: 三十万人民币左右。(300,000RMB more or less.)
In this example, 大概 implies the speaker is unclear or uncertain about the amount, or perhaps they don't remember. The use of 左右 implies a greater level of accuracy or certainty on the part of the speaker but they don't care to go into greater detail. The listener could press the speaker for more detail, in which case they would follow up with a more exact number if they were able.
The thing I rarely if ever hear 大概 used for is to express possibility. What this means is I don't think other words like 可能, 或许, and 也许 are similar in meaning. That said, I'm not a native speaker so I'm willing to allow for a number of use cases I'm not familiar with.
“大概”means “unsure/maybe/perhaps/probably”，不确定。 The same Chinese words can be:
1)或许
2)也许
3)可能
大概 has three basic meanings: 1 general (idea) 2 approximate 3 probably
Longmans Dictionary Contains the following comparison/warning about similar Chinese words: 【大抵•大概•大致】 dà dǐ / dà gài / dà zhì 都可作副詞﹐都表示對數量的估計和對情況的推測。區別在：①「大概」只表示約數；「大抵」能表示數量範圍﹐有大都﹑大多的意思；「大致」側重於事情的主要方面的情況。②在表示對情況的估計﹑揣測時﹐「大概」重在猜測；「大抵」偏重於肯定；「大致」偏重於大體上的意思。③「大概」和「大致」在口語﹑書面語中都較常用；「 大抵」一般用於書面。④「大概」還可以作名詞和形容詞﹐如「知道個大概」﹑「一個大概的數字」；「大抵」沒有名詞和形容詞用法；「大致」可作形容詞﹐如「大致的想法」﹐但不能作名詞。
While Guifan contains this note: 注意 ㊀跟“大致”不同。做副词时, “大概”侧重于估计, 既用于对数量的估计, 也用于对情况的估计; “大致”侧重于估算, 一般用于对数量的估算。㊁见大约的提示。
大约： 注意 跟“大概”不同。“大约”只作副词, 没有名词､区别词用法。
So while words like 大抵、大致、大约 may be similar to 大概 (in certain contexts) you still need to be careful how you use them.
Synonyms：好像，也许，八成，似乎，可能，大致。 Basic explanation:
Reference: Baidu Encyclopedia
大概 has the meaning of 'roughly'. Words with similar meaning are: 差不多
