What do "drop down", "burr" and "pounce on" mean?
Context:
"Yipee!" Wishbone dropped down and rolled in the leaves. He batted at a burr with his paw, while Yorkie pounced on his tail."

Question

What do "drop down", "burr" and "pounce on" mean?
Context:
"Yipee!" Wishbone dropped down and rolled in the leaves. He batted at a burr with his paw, while Yorkie pounced on his tail."

Answer

Drop down is like "fall down", but deliberate. Wishbone (I guess he's a dog) dropped from standing to lying position.

In this example, a burr (also "bur") is a kind of fruit from a tree, where the skin is dry and covered in rough hooks or prickles. Not really edible. So this burr was obviously with the dry leaves.

To "pounce on" something means to jump on something in order to seize it. The best image is a cat seizing (pouncing on) a mouse.

Answer

This is an excellent online dictionary which will help you with your question and others you might have in future: www.thefreedictionary.com

Answer

3- Pounce on
 pounce (on / upon sb/sth)
 to move suddenly forwards in order to attack or catch sb/sth:
The lion crouched ready to pounce. 
 The muggers pounced on her as she got out of the car. 
Owen pounced on the loose ball and scored.

PHRASAL VERBS
 'pounce on / upon sth
to quickly notice sth that sb has said or done, especially in order to criticize it
 SYN  seize on / upon:
His comments were pounced upon by the press.

Answer

2- Burr
 BURR (noun)
  The noun BURR has 5 senses:
1. seed vessel having hooks or prickles
2. rough projection left on a workpiece after drilling or cutting
3. United States politician who served as vice president under Jefferson; he mortally wounded his political rival Alexander Hamilton in a duel and fled south (1756-1836)
4. rotary file for smoothing rough edges left on a workpiece
5. small bit used in dentistry or surgery
  Familiarity information: BURR used as a noun is common.

• BURR (verb)
  The verb BURR has 1 sense:
1. remove the burrs from
  Familiarity information: BURR used as a verb is very rare.

http://www.audioenglish.net/dictionary/burr.htm

Answer

1-  Drop down 
Meaning:
Fall or drop to a lower place or level

Classified under:
Verbs of walking, flying, swimming

Synonyms:
drop down; sink; drop

Context example:
He sank to his knees

Hypernyms (to "drop down" is one way to...):
change posture (undergo a change in bodily posture)

Troponyms (each of the following is one way to "drop down"):
drop open; fall open (open involuntarily)
droop; flag; sag; swag (droop, sink, or settle from or as if from pressure or loss of tautness)
sag; sag down (cause to sag)