We are the more pleased to have its authenticity vouched for by this veracious witness. The underlined word means -

Veracious (adjective)
English Meaning: Precisely accurate; habitually speaking the truth.
Bangla Meaning: সত্য; যথার্থ; সত্যপরায়ণ; সত্যসন্ধ; সত্যনিষ্ঠ; সত্যবাদী।

Synonyms: Exact (যথাযথ), Literal (আক্ষরিক), Faithful (বিশ্বস্ত), Honest (সৎ), Truthful (সত্যপরায়ণ; সত্যবাদী)।
Antonyms: Untrue (অসত্য), Dishonest (অসৎ), Improper (অনুপযুক্ত), Fraudulent (প্রতারণামূলক), Mendacious (দুষ্টু)।
Other Forms:
- Veraciously (adverb) সত্যনিষ্ঠভাবে।
- Veracity [ভার‌্যাসাটি] (noun) [uncountable noun] সত্য; সত্যপরায়ণতা; সত্যসন্ধতা; সত্যনিষ্ঠা।
Example Sentence:
1. We are the more pleased to have its authenticity vouched for by this veracious witness.
2. It is such a rarity to discover an album that is held together by songs of veracious beauty.

Source: Website Lecture