The noun form of the word 'Mendacious' -

Mendacious (adjective)
English Meaning: Not telling the truth; lying.
Bangla Meaning: (আনুষ্ঠানিক) মিথ্যা; মিথ্যাবাদী: mendacious reports.

Synonyms: Untruthful (মিথ্যাবাদী), Dishonest (অসাধু), Deceitful (প্রতারণাপূর্ণ), Lying (মিথ্যা), Fraudulent (ধোঁকাবাজি)।

Antonyms: Truthful (সত্যনিষ্ঠ), Honest (সৎ), Veracious (সত্যনিষ্ঠ), Frank (নির্ভীক), Sincere (একনিষ্ঠ)।

Other Forms: 
- Mendaciously (adverb) অসত্যভাবে।
- Mendacity [মেন্‌ড্যাসাটি] (noun) (আনুষ্ঠানিক) [uncountable noun] মিথ্যা; [countable noun] (plural mendacities) অসত্য বিবরণ।

Example Sentence: 
1. That promise has been revealed as mendacious nonsense.
2. The newspaper story was mendacious and hurtful.

Source: Lecture.