Fabio M. Giacomini

This plugin adds a new field in every post, where you can write a text that will be inserted in the related meta tag, located in the head section.
The main options page of the plugin, provides you with a default text area, where you can insert a default description that will appear in case the field in post page is empty.

Single Post Meta Description

The easiest way to add in every post page a different meta description tag, located in html head.

Kunal Shivale

This plugin is for globally Meta Keyword and Meta Description. Once its configured it can be used in all pages.
It has below features: 
1. Add Meta Keyword 
2. Add Meta Description 
3. Add Meta Robots 
4. Add Meta Tags

Global Meta Keyword & Description

This plugin is for globally Meta Keyword and Meta Description. Once its configured it can be used in all pages.

Single Post Meta Description vs Global Meta Keyword & Description