Это чушь.

In Russian, the verb to be is usually omitted in the present tense.

So:

• Это чушь. = This is nonsense.
• literally: This — nonsense.

In past or future, forms of to be do appear indirectly through other structures:

• Это была чушь. = That was nonsense.
• Это будет чушь. = That will be nonsense.

So the missing is is completely normal Russian grammar.

This is a very common question.

Here, это does not agree with чушь in gender. In sentences like this, это often works as a fixed demonstrative meaning this, that, or even it in a general sense:

• Это книга. = This is a book.
• Это проблема. = This is a problem.
• Это чушь. = This is nonsense.

So even though чушь is feminine, это stays это.

You would use эта when it directly modifies a feminine noun:

• эта чушь = this nonsense
• эта книга = this book

So compare:

• Это чушь. = This is nonsense.
• Эта чушь раздражает меня. = This nonsense annoys me.

Чушь means nonsense, rubbish, trash, or absurdity depending on context.

It is used when something is silly, untrue, ridiculous, or not worth taking seriously.

Possible translations:

• That’s nonsense.
• That’s rubbish.
• That’s absurd.
• What nonsense.

It is fairly colloquial and expressive, but not obscene.

It is not a swear word, but it can sound dismissive or blunt.

Tone matters a lot:

• calm tone: That’s nonsense.
• annoyed tone: What rubbish.
• stronger tone: almost That’s crap, though чушь itself is usually a bit less vulgar than that

So it is not especially rude, but it can definitely sound critical.

It is in the nominative singular.

This sentence is a simple identification statement:

• Это = this/that/it
• чушь = nonsense

Russian often uses the nominative in this kind of present-tense sentence.

Also, чушь is a feminine noun ending in a soft sign, which is a common pattern for some feminine nouns:

• ночь
• вещь
• помощь
• чушь

A simple pronunciation guide is:

• Это ≈ EH-tuh
• чушь ≈ choosh

More carefully:

• э́то — stress on the first syllable
• чушь — one syllable, stressed

A rough full pronunciation is:

EH-tuh choosh

A few useful notes:

• ч is like ch in cheese
• у is like oo in boot
• ш is like sh in ship, but a bit harder/darker in Russian
• the final ь soft sign does not have its own sound, but it affects pronunciation slightly

The stress is:

• Э́то
• чу́шь

So the sentence is pronounced:

Э́то чу́шь.

Since чушь has only one syllable, that syllable is automatically stressed.

Yes. In many contexts, это can be translated as:

• this
• that
• it

So depending on the situation, Это чушь could mean:

• This is nonsense.
• That is nonsense.
• It’s nonsense.

Russian often relies more on context than English does.

Yes, but the neutral and most common order is:

• Это чушь.

You may also see:

• Чушь это.

That version is more marked and can sound emotional, emphatic, or literary, something like:

• Nonsense, that is.
• That’s nonsense.

For everyday use, stick with Это чушь.

To negate it:

• Это не чушь. = This is not nonsense.

To ask a yes/no question, Russian usually uses intonation:

• Это чушь? = Is this nonsense?

You can also make it more explicit:

• Это чушь или нет? = Is this nonsense or not?

So the structure stays very simple.

Usually, чушь behaves like an uncountable noun, similar to English nonsense.

So normally it means nonsense in a general sense:

• Это чушь. = This is nonsense.

Russian does not usually treat it as one nonsense / two nonsense things in basic usage.

If you want to refer to a specific foolish statement, Russian often still just uses чушь or switches to another noun depending on context, such as:

• глупость = a stupid thing / foolishness
• ерунда = nonsense / rubbish
• бред = delirium / absurd nonsense

Yes, several common ones:

• ерунда — nonsense, rubbish; very common and conversational
• бред — absurd nonsense, often stronger; literally also delirium
• глупость — stupidity, a stupid thing
• вздор — nonsense; a bit more bookish or old-fashioned in some contexts

So:

• Это чушь. = natural, colloquial, dismissive
• Это ерунда. = also very common, sometimes slightly lighter
• Это бред. = stronger, more forceful: That’s absurd / That’s insane nonsense

All can translate as nonsense, but the tone is slightly different.