From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Ταπεινόω (Strong'S #5013 — Verb — tapeinoo — tap-i-no'-o )

signifies "to make low, bring low," (a) of bringing to the ground, making level, reducing to a plain, as in  Luke 3:5; (b) metaphorically in the Active Voice, to bring to a humble condition, "to abase,"  2—Corinthians 11:7 , and in the Passive, "to be abased,"  Philippians 4:12; in  Matthew 23:12;  Luke 14:11;  18:14 , the AV has "shall be abased," the RV "shall be humbled." It is translated "humble yourselves" in the Middle Voice sense in  James 4:10;  1—Peter 5:6; "humble," in  Matthew 18:4;  2—Corinthians 12:21 and   Philippians 2:8 . See Humble , Low. Cp., tapeinos, "lowly," tapeinois, "humiliation," and tapeinophrosune, "humility."

King James Dictionary [2]

ABA'SE, Fr abaisser, from bas, low, or the bottom W. bais Latin and Gr. basis Eng. base It. Abbassare Sp. bare, low. See Abash.

1. The literal sense of abase is to lower or depress, to throw or cast down, as used by Bacon, "to abase the eye." But the word is seldom used in reference to material things. 2. To cast down to reduce low to depress to humble to degrade applied to the passions, rank, office, and condition in life.

Those that walk in pride he is able to abase.  Daniel 4 .

Whosoever exalteth himself shall be abased,  Matthew 23;  Job 40;  2 Corinthians 11.

Webster's Dictionary [3]

(1): (a.) To cast down or reduce low or lower, as in rank, office, condition in life, or estimation of worthiness; to depress; to humble; to degrade.

(2): (a.) To lower or depress; to throw or cast down; as, to abase the eye.

International Standard Bible Encyclopedia [4]

a - bās ´: The English rendition of שׁפּל , shāphēl ( Job 40:11;  Ezekiel 21:26 ), and of its derivative שׁפּל , shephal ( Daniel 4:37 ) = "bring down," "debase," "humble"; of ענה , ‛ānāh ( Isaiah 31:4 ) = "abase self," "afflict," "chasten self," "deal harshly with," etc.; and of ταπεινόω , tapeinóō = "to depress"; figure "to humiliate" (in condition or heart): "abase," "bring low," "humble self" ( Philippians 4:12 ). The word is always employed to indicate what should be done to or by him who nurtures a spirit and exhibits a demeanor contrary to the laudable humility which is a natural fruit of religion. Such a person is warned that the most extravagant audacity will not daunt Yahweh nor abate His vengeance ( Isaiah 31:4 ), and good men are exhorted to employ their powers to bring him low ( Job 40:11;  Ezekiel 21:26 ). If men are not able to curb the arrogant, God is ( Daniel 4:37 ); and He has so constituted the world, that sinful arrogance must fall ( Matthew 23:12 the King James Version;   Luke 14:11 the King James Version;   Luke 18:14 the King James Version).