Here's the list of Top 10 Words that I found hard to remember. I made a list during my preparation and these the harder one's that I found. All the words here are coming from different resources. Second list will be posted subsequently.
These are not the exact meanings, but I've written the meaning, as how we use them in context

aplomb
Confidence ; Stubborness

bestow
To give or to put for some use

garbled
Misinterpret or mislead

Extemporaneous
Done, spoken, performed,etc. without special advance preparation

Extirpate
To root up; Destroy

Indict
To formally charge or accuse of wrong-doing

Embryonic
In an early stage of development

Begrudge
To envy someone for possessing something

Impertinent
Improperly forward or bold

Transcendent
Beyond the range of normal human experience or range