En otras palabras, no podemos ir.

It is a very common linking expression meaning in other words. It signals that the speaker is about to restate, clarify, or sum up what was just said.

So En otras palabras, no podemos ir means something like:
To put it another way, we can't go.

It works much like English in other words.

Because palabras is a feminine plural noun, so the adjective has to agree with it.

• palabra = feminine singular
• palabras = feminine plural
• otra = feminine singular
• otras = feminine plural

So:

• otra palabra = another word
• otras palabras = other words

This is standard adjective agreement in Spanish.

It is both understandable word by word and also a fixed, natural expression.

Word by word:

• en = in
• otras = other
• palabras = words

But in real Spanish, En otras palabras is a set phrase used exactly like English in other words. So it is best to learn it as a chunk.

Because En otras palabras is an introductory phrase. In both Spanish and English, introductory phrases are often separated from the main clause with a comma.

So the structure is:

• En otras palabras, = introductory connector
• no podemos ir. = main statement

You will often see the comma here in careful, standard writing.

Podemos is the 1st person plural form of poder, which means to be able to or can.

Here it means we can.

So:

• puedo = I can
• puedes = you can
• puede = he/she/it can
• podemos = we can
• podéis = you all can (Spain)
• pueden = they/you all can

So no podemos = we cannot / we can't.

Because no usually goes directly before the conjugated verb in a normal negative sentence.

So:

• podemos ir = we can go
• no podemos ir = we cannot go

If you say podemos no ir, that usually means something slightly different: we can choose not to go or it is possible for us not to go. That is a more specific idea.

So in your sentence, no podemos ir is the normal way to say we can't go.

Because poder is a modal-type verb, and after it you normally use a second verb in the infinitive.

So:

• podemos ir = we can go
• puedo comer = I can eat
• pueden venir = they can come

This is similar to English can + base verb:

• we can go
• I can eat
• they can come

In Spanish, that second verb stays in the infinitive: ir, comer, venir, etc.

Because after poder, Spanish does not use a before the infinitive.

English often uses to with infinitives, but not after can:

• to go
• but we can go, not we can to go

Spanish works similarly here:

• ir = to go
• but podemos ir, not podemos a ir

So after poder, just use the infinitive directly.

Because Spanish often leaves out subject pronouns when the verb ending already makes the subject clear.

Podemos already tells you the subject is we.

So both are possible:

• No podemos ir.
• Nosotros no podemos ir.

The version without nosotros is more normal unless you want emphasis or contrast.

For example:

• Ellos sí pueden ir, pero nosotros no podemos ir.
  They can go, but we can't.

There, nosotros adds emphasis.

They are different ideas:

• no podemos ir = we can't go / we are not able to go
• no vamos a ir = we are not going to go / we won't go

So no podemos ir focuses on ability, possibility, or permission.
No vamos a ir focuses on a future plan or intention.

Examples:

• No podemos ir porque estamos trabajando.
  We can't go because we are working.
• No vamos a ir porque no queremos.
  We are not going to go because we don't want to.

Usually ir means to go, and the exact nuance depends on context.

In many situations, English might translate it as:

• go
• go there
• sometimes even leave

But if you specifically want to say leave, Spanish often uses:

• irse = to leave / to go away
• salir = to go out / to leave

So:

• No podemos ir = We can't go
• No podemos irnos = We can't leave
• No podemos salir = We can't go out / leave

Your sentence most naturally reads as we can't go.

Yes. Some common alternatives are:

• Es decir, ... = that is to say / that is
• O sea, ... = that is / I mean / in other words (very common in speech)
• Dicho de otro modo, ... = put another way

But En otras palabras is very clear and standard. It works well in both spoken and written Spanish.