Legal Question in Family Law in Texas

That is not a legal term. The closest definition might be in the Texas Family Code, section 161.001(1):

(A) voluntarily left the child alone or in the possession of another not the parent and expressed an intent not to return;

(B) voluntarily left the child alone or in the possession of another not the parent without expressing an intent to return, without providing for the adequate support of the child, and remained away for a period of at least three months;

(C) voluntarily left the child alone or in the possession of another without providing adequate support of the child and remained away for a period of at least six months;